WO2016067343A1

WO2016067343A1 - Laser device and extreme ultraviolet light generation device

Info

Publication number: WO2016067343A1
Application number: PCT/JP2014/078522
Authority: WO
Inventors: 野極　誠二
Original assignee: ギガフォトン株式会社
Priority date: 2014-10-27
Filing date: 2014-10-27
Publication date: 2016-05-06
Also published as: US20170181259A1; JPWO2016067343A1; US10165665B2; JP6434985B2

Abstract

The purpose of the present invention is to output laser light having desired characteristics at a desired timing. This laser device is a laser device to be used in tandem with an extreme ultraviolet light generation device that generates extreme ultraviolet light at a repetition frequency set in advance. The laser device may be provided with: semiconductor lasers that output laser light upon input of a trigger signal; optical switches that are disposed on the light path of the laser light and toggle between allowing the laser light to pass and not allowing the laser light to pass; and a control unit that outputs the trigger signal to the semiconductor lasers at a frequency that is an integer multiple of the repetition frequency and controls the optical switches such that the laser light passes at the repetition frequency.

Description

Laser apparatus and extreme ultraviolet light generation apparatus

The present disclosure relates to a laser device and an extreme ultraviolet light generation device.

In recent years, with the miniaturization of semiconductor processes, miniaturization of transfer patterns in photolithography of semiconductor processes has rapidly progressed. In the next generation, microfabrication of 70 nm to 45 nm, and microfabrication of 32 nm or less will be required. Therefore, for example, an extreme ultraviolet (EUV) light generation apparatus that generates extreme ultraviolet (EUV) light with a wavelength of about 13 nm and reduced projection reflective optics (Reduced Projection Reflective Optics) to meet the demand for fine processing of 32 nm or less Development of a combined exposure apparatus is expected.

As an EUV light generation apparatus, an LPP (Laser Produced Plasma) type apparatus using plasma generated by irradiating a target material with laser light, and DPP (plasma generated by discharge) are used. Three types of devices have been proposed: a device of the Discharge Produced Plasma method and a device of the SR (Synchrotron Radiation) method using orbital radiation.

US Patent Application Publication No. 2013/0148674 U.S. Patent No. 8311066 U.S. Patent Application Publication No. 2010/0193710 U.S. Patent Application Publication No. 2013/0032735

Overview

A laser device according to one aspect of the present disclosure is a laser device used with an extreme ultraviolet light generation device that generates extreme ultraviolet light at a preset repetition frequency, and outputs a laser beam when a trigger signal is input. A semiconductor laser, an optical switch disposed on an optical path of the laser beam, which switches whether or not to pass the laser beam, and the trigger signal is output to the semiconductor laser at a frequency that is an integral multiple of the repetition frequency; And a controller configured to control the optical switch such that the laser light passes at the repetition frequency.

A laser device according to one aspect of the present disclosure is a laser device used with an extreme ultraviolet light generation device that generates extreme ultraviolet light at a preset repetition frequency, and outputs a laser beam when a trigger signal is input. A semiconductor laser, an optical switch disposed on the optical path of the laser beam, which switches whether to pass the laser beam, and an output timing of the trigger signal to be output to the semiconductor laser in synchronization with the repetition frequency. The control unit may be changed based on the repetition frequency, and may control the optical switch such that the laser light passes at the repetition frequency.

A laser device according to one aspect of the present disclosure is a laser device used with an extreme ultraviolet light generation device that generates extreme ultraviolet light at a preset repetition frequency, and outputs a laser beam when a trigger signal is input. A semiconductor laser, an optical switch disposed on the optical path of the laser beam, which switches whether to pass the laser beam, and a pulse width of the trigger signal output to the semiconductor laser in synchronization with the repetition frequency The control unit may be changed based on the repetition frequency, and may control the optical switch such that the laser light passes at the repetition frequency.

In an extreme ultraviolet light generation device according to one aspect of the present disclosure, a semiconductor laser that outputs a laser light when a trigger signal is input, and whether it is disposed on the light path of the laser light and passes the laser light An optical switch for switching the light source, a control unit for outputting the trigger signal to the semiconductor laser at a frequency that is an integral multiple of the repetition frequency, and controlling the optical switch to pass the laser light at the repetition frequency; A target supply unit for supplying a target that emits extreme ultraviolet light when irradiated with light, to a chamber into which the laser light that has passed through the optical switch is introduced, at a frequency that is an integral multiple of the repetition frequency; You may have.

Several embodiments of the present disclosure are described below, by way of example only, with reference to the accompanying drawings.
FIG. 1 schematically shows the configuration of an exemplary LPP-type EUV light generation system. FIG. 2 shows the configuration of an EUV light generation system in which a specific configuration of a laser device is shown. FIG. 3A shows a diagram for explaining the detailed configuration of the first optical switch. FIG. 3B is a diagram for explaining the relationship between the incident timing of the pulse laser light to the Pockels cell and the voltage applied to the Pockels cell. FIG. 4 shows a diagram for explaining the detailed configuration of the regenerative amplifier. FIG. 5 shows a diagram for explaining the detailed configuration of the first QCL. FIG. 6 shows a diagram for explaining wavelength chirping generated in the first QCL. FIG. 7 shows the configuration of an EUV light generation system including the laser device of the first embodiment. FIG. 8 is a diagram for explaining the operation relating to the laser oscillation of the EUV light generation system including the laser device of the first embodiment. FIG. 9 shows the configuration of an EUV light generation system including the laser device of the second embodiment. FIG. 10 is a diagram for explaining the delay time added to the trigger signal output from the control unit included in the laser apparatus of the second embodiment. FIG. 11 shows the result of measuring the relationship between the light emission delay time of QCL and the repetition frequency. FIG. 12 is a diagram for explaining the pulse width of the trigger signal output from the control unit included in the laser device of the third embodiment. FIG. 13 shows the relationship between the repetition frequency of the trigger signal output to the QCL and the pulse width. FIG. 14 is a block diagram showing a hardware environment of each control unit. FIG. 15 shows a diagram for explaining a modified example of the laser apparatus related to the generation of the trigger signal.

Embodiment

Contents
1. Overview 2. Explanation of terms 3. Overall Description of EUV Light Generation System 3.1 Configuration 3.2 Operation 4. Laser apparatus used together with an EUV light generation apparatus 4.1 Configuration 4.2 Operation 4.3 Optical Switch 4.4 Regenerative Amplifier 4.5 Quantum Cascade Laser 5. Problem 6. EUV light generation system including the laser device of the first embodiment 6.1 Configuration 6.2 Operation 6.3 Operation 7. EUV light generation system including the laser device of the second embodiment EUV light generation system including the laser device of the third embodiment Others 9.1 Hardware environment of each control unit 9.2 Modification of laser device for generation of trigger signal 9.3 Other modification

Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. The embodiments described below illustrate some examples of the present disclosure and do not limit the content of the present disclosure. Further, all the configurations and operations described in each embodiment are not necessarily essential as the configurations and operations of the present disclosure. In addition, the same reference numerals are given to the same components, and the overlapping description is omitted.

[1. Overview]
The present disclosure may at least disclose the following embodiments.

The laser apparatus 3 is a laser apparatus 3 used together with the EUV light generation apparatus 1 for generating the EUV light 252 at a preset repetition frequency, and the first to fourth QCLs 311 to 314 for outputting the pulsed laser light 30, and the pulse The first to fourth

optical switches

321, 322, 373 and 374 which are disposed on the optical path of the laser beam 30 and switch whether the pulse laser beam 30 is allowed to pass or not, and the pulse laser beam 30 has an integer multiple of the repetition frequency A control unit 330 that controls the first to fourth QCLs 311 to 314 to be output, and controls the first to fourth

optical switches

321, 322, 373 and 374 such that the pulse laser beam 30 passes at the repetition frequency; May be provided.
With such a configuration, the laser device 3 can output the pulse laser beam 31 having a desired characteristic at a desired timing even when the operating condition is changed.

[2. Explanation of terms]
The "target" is an irradiation target of the laser beam introduced into the chamber. The target irradiated with the laser light is plasmatized to emit EUV light.
"Droplet" is a form of target supplied into the chamber.
The “optical path axis” is an axis passing through the center of the cross section of the laser beam along the traveling direction of the laser beam.
The "optical path" is a path through which laser light passes. The optical path may include an optical path axis.
The “upstream side” is the side closer to the oscillator of the laser light along the optical path of the laser light.
The “downstream side” is the side far from the laser light oscillator along the optical path of the laser light.
The “optical switch” is an element that switches whether to change the optical path of the incident laser light. Thereby, the optical switch may switch whether to pass the incident laser light. The optical switch may change the optical path of the incident laser light according to the electrical signal.

[3. Overall description of EUV light generation system]
[3.1 Configuration]
FIG. 1 schematically shows the configuration of an exemplary LPP EUV light generation system.
The EUV light generation device 1 may be used with at least one laser device 3. In the present application, a system including the EUV light generation apparatus 1 and the laser apparatus 3 is referred to as an EUV light generation system 11. As shown in FIG. 1 and described in detail below, the EUV light generation system 1 may include a chamber 2 and a target supply unit 26. Chamber 2 may be sealable. The target supply unit 26 may be attached, for example, to penetrate the wall of the chamber 2. The material of the target material supplied from the target supply unit 26 may include, but is not limited to, tin, terbium, gadolinium, lithium, xenon, or a combination of any two or more thereof.

The wall of the chamber 2 may be provided with at least one through hole. A window 21 may be provided in the through hole, and the pulse laser beam 32 output from the laser device 3 may be transmitted through the window 21. Inside the chamber 2, for example, an EUV collector mirror 23 having a spheroidal reflecting surface may be disposed. The EUV collector mirror 23 may have first and second focal points. On the surface of the EUV collector mirror 23, for example, a multilayer reflective film in which molybdenum and silicon are alternately stacked may be formed. The EUV collector mirror 23 is preferably arranged, for example, such that its first focal point is located at the plasma generation region 25 and its second focal point is located at the intermediate focusing point (IF) 292. A through hole 24 may be provided in the central portion of the EUV collector mirror 23, and the pulse laser beam 33 may pass through the through hole 24.

The EUV light generation apparatus 1 may include an EUV light generation controller 5, a target sensor 4 and the like. The target sensor 4 may have an imaging function, and may be configured to detect the presence, trajectory, position, velocity and the like of the target 27.

In addition, the EUV light generation apparatus 1 may include a connection part 29 that brings the inside of the chamber 2 into communication with the inside of the exposure apparatus 6. Inside the connection portion 29, a wall 291 having an aperture 293 may be provided. The wall 291 may be arranged such that its aperture 293 is located at the second focus position of the EUV collector mirror 23.

Furthermore, the EUV light generation apparatus 1 may include a laser light traveling direction control unit 34, a laser light collecting mirror 22, a target collecting unit 28 for collecting the target 27, and the like. The laser light traveling direction control unit 34 may include an optical element for defining the traveling direction of the laser light, and an actuator for adjusting the position, attitude, and the like of the optical element.

[3.2 Operation]
Referring to FIG. 1, the pulse laser beam 31 output from the laser device 3 may pass through the window 21 as the pulse laser beam 32 and enter the chamber 2 through the laser beam direction control unit 34. The pulsed laser beam 32 may travel along the at least one laser beam path in the chamber 2, be reflected by the laser beam focusing mirror 22, and be irradiated to the at least one target 27 as the pulsed laser beam 33.

The target supply unit 26 may be configured to output the target 27 toward the plasma generation region 25 inside the chamber 2. The target 27 may be irradiated with at least one pulse included in the pulsed laser light 33. The target 27 irradiated with the pulsed laser light is plasmatized, and the EUV light 251 can be emitted from the plasma along with the emission of light of other wavelengths. The EUV light 251 may be selectively reflected by the EUV collector mirror 23. The EUV light 252 reflected by the EUV collector mirror 23 may be collected at an intermediate collection point 292 and output to the exposure apparatus 6. Note that a plurality of pulses included in the pulsed laser light 33 may be irradiated to one target 27.

The EUV light generation controller 5 may be configured to control the entire EUV light generation system 11. The EUV light generation controller 5 may be configured to process image data or the like of the target 27 captured by the target sensor 4. In addition, the EUV light generation controller 5 may perform at least one of timing control for outputting the target 27 and control of the output direction of the target 27, for example. Furthermore, the EUV light generation controller 5 performs at least one of, for example, control of the output timing of the laser device 3, control of the traveling direction of the pulse laser beam 32, and control of the focusing position of the pulse laser beam 33. It is also good. The various controls described above are merely exemplary, and other controls may be added as needed.

[4. Laser apparatus used together with EUV light generation apparatus]
[4.1 Configuration]
The specific configuration of the laser apparatus 3 used together with the EUV light generation apparatus 1 will be described with reference to FIG.
FIG. 2 shows the configuration of the EUV light generation system 11 in which the specific configuration of the laser device 3 is shown.
The EUV light generation system 11 of FIG. 2 may include the EUV light generation apparatus 1 and the laser device 3 as in the EUV light generation system 11 shown in FIG. 1.
In the configuration of the EUV light generation system 11 of FIG. 2, the description of the same configuration as that of the EUV light generation system 11 shown in FIG. 1 will be omitted.

The laser device 3 includes an oscillator 310, a first optical switch 321, a second optical switch 322, a control unit 330, first to fourth amplifiers 351 to 354, and first to fourth RF (Radio Frequency) power supplies 361. To 364, a regenerative amplifier 370, and an RF (Radio Frequency) power supply 380.
In the present embodiment, the number of amplifiers provided in the laser device 3 is described as being four units of the first to fourth amplifiers 351 to 354 for the sake of convenience, but it is not particularly limited. It may be. The number of first to fourth RF power supplies 361 to 364 may be the same as the number of first to fourth amplifiers 351 to 354.
The oscillator 310 and the first to fourth amplifiers 351 to 354 may constitute a master oscillator power amplifier (MOPA) system.

The oscillator 310 may be a master oscillator that constitutes the MOPA system.
The oscillator 310 may output pulsed laser light 30.
The oscillator 310 may include a semiconductor laser and an optical path regulator 315.

The semiconductor laser included in the oscillator 310 may be a quantum cascade laser (QCL).
The semiconductor laser included in the oscillator 310 may be a distributed feedback semiconductor laser.
The semiconductor laser included in the oscillator 310 may be a semiconductor laser that outputs pulsed laser light of a wavelength included in a wavelength range that can be amplified by a laser amplifier using a CO ₂ gas as an amplification medium.

The oscillator 310 may include a plurality of semiconductor lasers.
The plurality of semiconductor lasers included in the oscillator 310 may be the first to fourth QCLs 311 to 314.
In the present embodiment, although the number of QCLs included in the oscillator 310 is described as four units of the first to fourth QCLs 311 to 314 for convenience, it is not particularly limited, and may be one or more. It is also good.
Each of the first to fourth QCLs 311 to 314 may be connected to the control unit 330. Under control of the control unit 330, each of the first to fourth QCLs 311 to 314 may perform laser oscillation and output pulsed laser light.

Each of the first to fourth QCLs 311 to 314 may output pulsed laser light of a wavelength different from each other.
The respective different wavelengths of the pulsed laser light output from the first to fourth QCLs 311 to 314 may be different from each other in the wavelength range that can be amplified in the laser amplifier.
In the present disclosure, a wavelength region that can be amplified by a laser amplifier provided subsequent to the first to fourth QCLs 311 to 314 among the wavelength regions of pulsed laser light output from each of the first to fourth QCLs 311 to 314 Is also referred to as “amplified wavelength region”.
Each of the first to fourth QCLs 311 to 314 may output linearly polarized pulsed laser light.
The pulsed laser light output from each of the first to fourth QCLs 311 to 314 may be incident on the optical path controller 315.
The detailed configurations of the first to fourth QCLs 311 to 314 will be described later with reference to FIG.

The optical path adjuster 315 may superimpose the optical paths of the pulsed laser light output from the first to fourth QCLs 311 to 314 substantially on one optical path and output the optical path as the pulsed laser light 30.
The optical path adjuster 315 may include an optical system (not shown).
The optical system included in the optical path adjuster 315 may be provided on the optical path of the pulse laser beam output from each of the first to fourth QCLs 311 to 314 and downstream of the first to fourth QCLs 311 to 314. .
The pulsed laser light 30 output through one optical path by the optical path adjuster 315 may enter the first optical switch 321.

The first optical switch 321 may switch whether to allow the incident pulse laser beam 30 to pass.
The first optical switch 321 may be disposed on the optical path of the pulsed laser light 30 output from the optical path adjuster 315.
The first optical switch 321 may be connected to the controller 330. The first optical switch 321 may switch whether to pass the pulse laser beam 30 under the control of the control unit 330.
The pulsed laser light 30 that has passed through the first optical switch 321 may be incident on the regenerative amplifier 370.
The detailed configuration of the first optical switch 321 will be described later with reference to FIGS. 3A and 3B.

The regenerative amplifier 370 may amplify the incident pulse laser beam 30 and output it at a specific timing.
The regenerative amplifier 370 may be disposed on the optical path of the pulsed laser light 30 that has passed through the first optical switch 321.
The regenerative amplifier 370 may include a resonator mirror 371, a resonator mirror 372, a third optical switch 373, a fourth optical switch 374, and an amplifier 375.

The resonator mirrors 371 and 372 may constitute an optical resonator of the regenerative amplifier 370.
The resonator mirrors 371 and 372 may reflect the pulsed laser light 30 so that the pulsed laser light 30 incident on the regenerative amplifier 370 reciprocates between the resonator mirrors 371 and 372.

The amplifier 375 may amplify the pulsed laser light 30 every time the pulsed laser light 30 reciprocates between the resonator mirrors 371 and 372.
The amplifier 375 may be a laser amplifier using CO ₂ gas as an amplification medium.
The amplifier 375 may include a pair of discharge electrodes not shown.
Each of the pair of discharge electrodes included in amplifier 375 may be connected to RF power supply 380. The amplifier 375 may amplify the pulsed laser light 30 in accordance with the discharge voltage supplied from the RF power supply 380.

Each of the third and fourth

optical switches

373 and 374 may switch whether to change the optical path of the incident pulse laser beam 30.
Each of the third and fourth

optical switches

373 and 374 may be connected to the controller 330. Each of the third and fourth

optical switches

373 and 374 may switch whether to change the optical path of the pulsed laser light 30 under the control of the control unit 330. Thus, each of the third and fourth

optical switches

373 and 374 may guide the incident pulse laser beam 30 into the regenerative amplifier 370 and cause the regenerative amplifier 370 to output it at a specific timing.

The pulsed laser light 30 amplified by the regenerative amplifier 370 may be incident on the second optical switch 322 through the high reflection mirror.
The detailed configuration of the regenerative amplifier 370 will be described later with reference to FIG.

The RF power supply 380 may be a power supply that supplies a high frequency discharge voltage to the amplifier 375 included in the regenerative amplifier 370.
The RF power supply 380 may be connected to the controller 330. The RF power supply 380 may supply the discharge voltage to the amplifier 375 under the control of the control unit 330.

The second optical switch 322 may be an optical switch that switches whether to allow the incident pulse laser beam 30 to pass.
The second optical switch 322 may be disposed on the optical path of the pulsed laser light 30 output from the regenerative amplifier 370.
The second optical switch 322 may be connected to the controller 330. The second optical switch 322 may switch whether to pass the pulse laser beam 30 under the control of the control unit 330.
The pulsed laser light 30 that has passed through the second optical switch 322 may be incident on the first to fourth amplifiers 351 to 354.
The detailed configuration of the second optical switch 322 will be described later with reference to FIGS. 3A and 3B.
Further, a plurality of second optical switches 322 may be provided in the laser device 3. Each of the plurality of second optical switches 322 may be disposed downstream of each of the regenerative amplifier 370 and the first to fourth amplifiers 351 to 354.

The first to fourth amplifiers 351 to 354 may be power amplifiers constituting an MOPA system.
Each of the first to fourth amplifiers 351 to 354 may be a laser amplifier including a pair of discharge electrodes and using CO ₂ gas as an amplification medium. Each of the first to fourth amplifiers 351 to 354 may be either a slab amplifier, a three-axis orthogonal amplifier, or a high speed axial flow amplifier.

The first to fourth amplifiers 351 to 354 may sequentially amplify the pulsed laser light 30 that has passed through the second optical switch 322.
Specifically, each of the first to fourth amplifiers 351 to 354 receives respective pulse laser beams output from the former stage regenerative amplifier 370 or the first to third amplifiers 351 to 353 disposed on the upstream side of each of the first to fourth amplifiers 351 to 354. 30 may be incident. Each of the first to third amplifiers 351 to 353 may amplify each incident pulsed laser beam 30 and output the amplified pulse laser light 30 to the second to fourth amplifiers 352 to 354 disposed downstream of the pulse laser beam 30. The fourth amplifier 354 at the final stage may amplify the incident pulse laser beam 30 and output the amplified pulse laser beam 30 to the outside of the laser device 3 as the pulse laser beam 31.

Each of the first to fourth amplifiers 351 to 354 may be connected to each of the first to fourth RF power supplies 361 to 364.
Each of the first to fourth amplifiers 351 to 354 may amplify the incident pulsed laser light 30 according to the discharge current supplied from each of the first to fourth RF power supplies 361 to 364.

The first to fourth RF power supplies 361 to 364 may be power supplies for supplying discharge current to the first to fourth amplifiers 351 to 354.
Each of the first to fourth RF power supplies 361 to 364 may be connected to the control unit 330. Each of the first to fourth RF power supplies 361 to 364 may supply a discharge current to each of the first to fourth amplifiers 351 to 354 under the control of the control unit 330.

Here, an EUV light output command signal may be transmitted from the exposure apparatus control unit 61 to the EUV light generation controller 5 included in the EUV light generation apparatus 1 used together with the laser device 3.
The EUV light output command signal may be a signal indicating a control command related to the output of the EUV light 252.
The EUV light output command signal may include various target values such as a target output start timing of the EUV light 252, a target repetition frequency, and a target pulse energy. Various target values of the EUV light 252 can be set to the EUV light generation controller 5 by transmitting the EUV light output command signal.

The EUV light generation controller 5 may generate a target supply signal based on the EUV light output command signal transmitted from the exposure apparatus controller 61 and output the target supply signal to the target supply unit 26.
The target supply signal may be a signal indicating a control command related to the output of the droplet 271 into the chamber 2. The target supply signal may be a signal that controls the operation of the target supply unit 26 so that the droplet 271 is output according to various target values included in the EUV light output command signal.
The target supply signal may include various target values such as the target diameter of the droplet 271. The various target values of the droplet 271 may be values determined according to various target values included in the EUV light output command signal.
The EUV light generation controller 5 may determine the target output start timing and the target repetition frequency of the droplet 271 according to the target output start timing and the target repetition frequency of the EUV light 252 included in the EUV light output command signal. .
The target repetition frequency of the droplet 271 may have the same value as the target repetition frequency of the EUV light 252. The target output start timing of the droplet 271 may be a value determined according to the target output start timing of the EUV light 252.
The EUV light generation controller 5 may output a target supply signal to the target supply unit 26 according to the target output start timing and the target repetition frequency of the droplet 271 determined.

Further, a droplet detection signal may be input from the target sensor 4 to the EUV light generation controller 5.
The droplet detection signal may be a detection signal indicating that the droplet 271 which is the target 27 supplied from the target supply unit 26 to the plasma generation region 25 is output into the chamber 2.
The droplet 271 can be output from the target supply unit 26 based on the target output start timing of the EUV light 252 and the target supply signal reflecting the target repetition frequency included in the EUV light output command signal. The droplets 271 output from the target supply unit 26 based on the target supply signal can be detected by the target sensor 4 for each output. The droplet detection signal can be output from the target sensor 4 to the EUV light generation controller 5 each time the droplet 271 is detected.
At this time, the output interval of the droplet 271 may not be strictly constant but may be accompanied by a certain degree of instability. For this reason, the repetition frequency of the droplet detection signal may slightly fluctuate slightly, although it becomes approximately the target repetition frequency of the EUV light 252.
In the following description, the expression “approximately the same value as the target repetition frequency of the EUV light 252” or the expression “repetition frequency reflecting the target repetition frequency of the EUV light 252” is used. Although these expressions are strictly different from the target repetition frequency of the EUV light 252, they are used in cases where they can be regarded substantially as the target repetition frequency of the EUV light 252. The expression “approximately the same value as the master repetition frequency” described later and the expression “the repetition frequency reflecting the master repetition frequency” described later may be the same.
A droplet detection signal reflecting an EUV light output command signal can be input to the EUV light generation controller 5. The repetition frequency of the droplet detection signal may be substantially the same value as the target repetition frequency of the EUV light 252.

In addition, the EUV light generation controller 5 may generate a laser output signal based on the droplet detection signal reflecting the EUV light output command signal, and may output the generated laser output signal to the controller 330.
The laser output signal may be a signal indicating a control command related to the output of the pulse laser beam 31. The laser output signal may be a signal that controls the operation of the laser device 3 so that the pulse laser beam 31 is output according to various target values of the EUV light 252 included in the EUV light output command signal.
The laser output signal may include various target values such as target pulse energy of the pulse laser beam 31. The target pulse energy of the pulsed laser light 31 may be a value determined according to the target pulse energy of the EUV light 252.
The EUV light generation controller 5 outputs the laser output signal to the controller 330 for each pulse at a timing delayed by a predetermined delay time after the droplet detection signal reflecting the EUV light output command signal is input. It is also good.
The hardware configuration of the EUV light generation controller 5 will be described later with reference to FIG.

On the other hand, the controller 330 may be connected to the EUV light generation controller 5, and may receive the laser output signal output from the EUV light generation controller 5.
The control unit 330 may control the operation of each component included in the laser device 3 based on the laser output signal.

The control unit 330 may output a trigger signal to each of the first to fourth QCLs 311 to 314 based on the laser output signal.
The control unit 330 may output a trigger signal to each of the first to fourth QCLs 311 to 314 in each pulse in synchronization with the timing when the laser output signal is input.
The trigger signal may be a signal for giving an opportunity to cause each of the first to fourth QCLs 311 to 314 to perform laser oscillation to output pulsed laser light.
The repetition frequency of the trigger signal may define the repetition frequency of each of the first to fourth QCLs 311 to 314. The repetition frequency of the trigger signal may be the same value as the repetition frequency of the droplet detection signal.
The timing at which the trigger signal is output may define the timing at which the operation related to the laser oscillation of each of the first to fourth QCLs 311 to 314 is started.
Each of the first to fourth QCLs 311 to 314 can perform laser oscillation at the repetition frequency of the trigger signal to output pulsed laser light.

The trigger signal may include the set value of the excitation current supplied to each of the first to fourth QCLs 311 to 314.
The set value of the excitation current included in the trigger signal is determined based on the target pulse energy of the pulse laser beam 31 included in the laser output signal and the pulse energy of the pulse laser beam 30 measured by an energy monitor not shown. It is also good.
Each of the first to fourth QCLs 311 to 314 can output a pulsed laser beam by performing laser oscillation with an excitation current corresponding to the set value included in the input trigger signal.

The control unit 330 may output a trigger signal to each of the first to fourth QCLs 311 to 314 at a timing delayed by a predetermined delay time from the timing when the laser output signal is input from the EUV light generation controller 5.
The delay times added to the trigger signal may be delay times Dq1 to D4 different for each of the trigger signals output to the first to fourth QCLs 311 to 314, respectively.
As described above, the amplification wavelength regions corresponding to the pulsed laser beams output from the first to fourth QCLs 311 to 314 may be different from each other. The timings at which pulse laser beams having different wavelengths are output from the first to fourth QCLs 311 to 314 may be different from one another.
The lengths of the delay times Dq1 to Dq4 may be determined so that pulse laser beams having wavelengths in the amplification wavelength region are output from the first to fourth QCLs 311 to 314 at substantially the same timing.

Also, the control unit 330 may output a drive signal to each of the first to fourth

optical switches

321, 322, 373 and 374 based on the laser output signal.
The control unit 330 may output a drive signal to each of the first to fourth

optical switches

321, 322, 373 and 374 in synchronization with the timing when the laser output signal is input from the EUV light generation controller 5. .
The first to fourth

optical switches

321, 322, 373 and the drive signal to the optical switch allow the pulse laser beam 30 incident on the first to fourth

optical switches

321, 322, 373 and 374 to pass. It may be a signal that controls the operation of 374.

The control unit 330 drives the drive signals to the first to fourth

optical switches

321, 322, 373 and 374 at timings delayed by a predetermined delay time from the timing when the laser output signal is input from the EUV light generation control unit 5. May be output.
The delay times added to these drive signals may be delay times Dp1 to D4 different for each of the drive signals output to the first to fourth

optical switches

321, 322, 373 and 374. .
The lengths of the delay times Dp1 to 4 are the same as the first to fourth

optical switches

321, 322, 373 and the pulse laser light having the wavelength of the amplification wavelength region output from the first to fourth QCLs 311 It may be defined to be able to pass each of 374.

Further, the control unit 330 may output a voltage setting signal to the RF power supply 380 based on the laser output signal.
The control unit 330 may output a voltage setting signal to the RF power supply 380 in synchronization with the timing when the laser output signal is input from the EUV light generation control unit 5.
The voltage setting signal output to the RF power supply 380 may be a signal for setting the setting value of the discharge voltage supplied to the amplifier 375 of the regenerative amplifier 370 to the RF power supply 380.
The setting value of the discharge voltage included in the voltage setting signal is the target pulse energy of the pulse laser beam 31 included in the laser output signal and the pulse energy of the amplified pulse laser beam 30 measured by an energy monitor (not shown). It may be determined based on.
The RF power supply 380 can supply a discharge voltage corresponding to the setting value included in the input voltage setting signal to the amplifier 375 of the regenerative amplifier 370. The amplifier 375 of the regenerative amplifier 370 can amplify the pulsed laser light 30 incident on the regenerative amplifier 370 according to the supplied discharge voltage.

Further, the control unit 330 may output a current setting signal to each of the first to fourth RF power supplies 361 to 364 based on the laser output signal.
The control unit 330 may output the current setting signal to each of the first to fourth RF power supplies 361 to 364 in synchronization with the timing when the laser output signal is input from the EUV light generation controller 5.
The current setting signal output to each of the first to fourth RF power supplies 361 to 364 sets the setting value of the discharge current supplied to the first to fourth amplifiers 351 to 354 to the first to fourth RF power supplies 361 to 364 It may be a signal to be set.
The setting value of the discharge current included in the current setting signal is the target pulse energy of the pulse laser beam 31 included in the laser output signal and the pulse energy of the amplified pulse laser beam 30 measured by an energy monitor (not shown). It may be determined based on.
Each of the first to fourth RF power supplies 361 to 364 can supply a discharge current corresponding to the setting value included in the input current setting signal to each of the first to fourth amplifiers 351 to 354. Each of the first to fourth amplifiers 351 to 354 can amplify the pulsed laser light 30 incident on each of the first to fourth amplifiers 351 to 354 in accordance with the supplied discharge current.
The hardware configuration of the control unit 330 will be described later with reference to FIG.

The other configuration of the EUV light generation system 11 may be similar to the configuration of the EUV light generation system 11 shown in FIG. 1.

[4.2 Operation]
The operation related to the laser oscillation of the laser device 3 will be described with reference to the operation of the EUV light generation device 1 used together with the laser device 3.
In the operation of the EUV light generation system 11 of FIG. 2, the description of the same operation as that of the EUV light generation system 11 shown in FIG. 1 will be omitted.

The EUV light generation controller 5 may generate a target supply signal based on the EUV light output command signal transmitted from the exposure apparatus controller 61 and output the target supply signal to the target supply unit 26.
The target supply unit 26 can output the droplet 271 to the plasma generation region 25 in the chamber 2 based on the target supply signal. The target sensor 4 can detect the droplet 271 output into the chamber 2 and output a droplet detection signal to the EUV light generation controller 5.
The EUV light generation controller 5 may newly generate a target supply signal based on the EUV light output command signal and the droplet detection signal, and output the target supply signal to the target supply unit 26.

In addition, the EUV light generation controller 5 may generate a laser output signal based on the droplet detection signal output from the target sensor 4 and output the laser output signal to the controller 330.

The control unit 330 may determine the delay times Dq1 to D4 added to the trigger signals output to the first to fourth QCLs 311 to 314 based on the laser output signal.
The control unit 330 may determine the delay times Dp1 to D4 to be added to the drive signals output to the first to fourth

optical switches

321, 322, 373 and 374 based on the laser output signal. .
The control unit 330 may determine the setting value of the excitation current included in the trigger signal output to the first to fourth QCLs 311 to 314 based on the laser output signal.
The control unit 330 may determine the setting value of the discharge voltage included in the voltage setting signal output to the RF power supply 380 based on the laser output signal.
The control unit 330 may determine the set value of the discharge current included in the current setting signal output to the first to fourth RF power supplies 361 to 364 based on the laser output signal.

The control unit 330 may output a voltage setting signal including the determined setting value of the discharge voltage to the RF power supply 380.
The RF power supply 380 may supply a discharge voltage to the discharge electrode of the amplifier 375 of the regenerative amplifier 370 based on the input voltage setting signal.
The control unit 330 may output a current setting signal including the determined setting value of the discharge current to the first to fourth RF power supplies 361 to 364.
The first to fourth RF power supplies 361 to 364 may supply a discharge current to the discharge electrodes of the first to fourth amplifiers 351 to 354, based on the input current setting signal.

The control unit 330 outputs the trigger signal including the determined setting value of the excitation current to each of the first to fourth QCLs 311 to 314 at a timing delayed by the delay time Dq1 to 4 from the timing when the laser output signal is input. You may
Each of the first to fourth QCLs 311 to 314 can output pulsed laser light based on the input trigger signal. The optical path adjuster 315 may superimpose the optical paths of the pulsed laser light output from the first to fourth QCLs 311 to 314 substantially on one optical path, and may output the optical path as the pulsed laser light 30 to the first optical switch 321. .

The control unit 330 may output the drive signal to the first optical switch 321 to the first optical switch 321 at a timing delayed by the delay time Dp1 from the timing when the laser output signal is input.
The first optical switch 321 can pass the incident pulse laser beam 30 based on the input drive signal, and can output it to the regenerative amplifier 370.

The control unit 330 may output the drive signal to the third optical switch 373 to the third optical switch 373 at a timing delayed by the delay time Dp3 from the timing when the laser output signal is input.
The third optical switch 373 can change the optical path of the incident pulse laser beam 30 based on the input drive signal, and introduce the pulse laser beam 30 into the regenerative amplifier 370. The pulsed laser light 30 introduced into the regenerative amplifier 370 can be amplified each time it passes through the amplifier 375 while reciprocating between the resonator mirrors 371 and 372.

The control unit 330 may output the drive signal to the fourth optical switch 374 to the fourth optical switch 374 at a timing delayed by the delay time Dp4 from the timing when the laser output signal is input.
The fourth optical switch 374 can change the optical path of the incident pulse laser beam 30 based on the input drive signal, and can output it from the regenerative amplifier 370 to the high reflection mirror. The high reflection mirror can reflect the incident pulse laser beam 30 and output it to the second optical switch 322.

The control unit 330 may output the drive signal to the second optical switch 322 to the second optical switch 322 at a timing delayed by the delay time Dp2 from the timing when the laser output signal is input.
The second optical switch 322 can pass the incident pulse laser beam 30 based on the input drive signal and can output the pulse laser beam 30 to the first amplifier 351. Each of the first to fourth amplifiers 351 to 354 can sequentially amplify the pulse laser beam 30. The pulsed laser light 30 amplified by the fourth amplifier 354 at the final stage can be output to the outside of the laser device 3 as a pulsed laser light 31.

The pulsed laser light 31 output from the laser device 3 can be introduced into the chamber 2 as pulsed laser light 32 via the laser light traveling direction control unit 34 and the window 21 of the EUV light generation apparatus 1. The pulsed laser beam 32 introduced into the chamber 2 may be focused on the plasma generation region 25 as a pulsed laser beam 33 by the laser beam focusing mirror 22. The pulsed laser light 33 focused on the plasma generation region 25 can irradiate the droplet 271 output from the target supply unit 26 to the plasma generation region 25. The droplet 271 can be plasmatized to emit light including the EUV light 251 when the pulsed laser light 33 is irradiated. The EUV light 251 can be selectively reflected by the EUV collector mirror 23 and output to the exposure apparatus 6 as the EUV light 252.

Other operations of the EUV light generation system 11 may be similar to the operations of the EUV light generation system 11 shown in FIG. 1.

[4.3 Optical switch]
The detailed configuration of the first and second

optical switches

321 and 322 will be described with reference to FIGS. 3A and 3B.
The internal configuration of each of the first and second

optical switches

321 and 322 may be substantially the same as each other.
In the description of FIGS. 3A and 3B, the first optical switch 321 will be described as an example.
FIG. 3A shows a diagram for explaining the detailed configuration of the first optical switch 321. As shown in FIG. FIG. 3B is a diagram for explaining the relationship between the incident timing of the pulse laser light 30 to the Pockels cell 321 a and the voltage applied to the Pockels cell 321 a.

The first optical switch 321 may be configured using an electro-optical element.
The first optical switch 321 may include a Pockels cell 321a, a polarizer 321b, a polarizer 321c, and a power supply 321d.

The

polarizers

321 b and 321 c may transmit a specific linear polarization component of the incident pulse laser beam 30 and reflect the other linear polarization components.
The

polarizers

321 b and 321 c may be disposed to be substantially orthogonal to the optical path axis of the incident pulse laser beam 30.
The

polarizers

321 b and 321 c may be arranged in a cross nicol state on the optical path of the incident pulse laser beam 30.
For example, the polarizer 321 b may transmit the pulse laser beam 30 which is linearly polarized light in the Y direction, and may reflect the pulse laser beam 30 which is linearly polarized light in the X direction. The polarizer 321 c may transmit, for example, the pulse laser beam 30 in linear polarization in the X direction and may reflect the pulse laser beam 30 in linear polarization in the Y direction.

The power supply 321 d may be a power supply that applies a voltage to the Pockels cell 321 a.
The power supply 321 d may apply a voltage to the Pockels cell 321 a so that an electric field in a direction substantially orthogonal to the traveling direction of the pulsed laser light 30 incident on the Pockels cell 321 a is generated in the Pockels cell 321 a.
The power supply 321 d may be connected to the control unit 330. The drive signal to the first optical switch 321 output from the control unit 330 may be input to the power supply 321 d. The power supply 321 d may apply an applied voltage to the Pockels cell 321 a at the voltage value, the pulse width, and the application timing of the applied voltage specified by the input drive signal.

The Pockels cell 321a may be formed using a birefringent material.
Pockels cell 321a may be disposed between

polarizers

321b and 321c. The Pockels cell 321 a may be disposed such that the surface on which the pulse laser beam 30 is incident is substantially orthogonal to the optical path axis of the pulse laser beam 30.
The refractive index of the Pockels cell 321a may change according to the applied voltage by the Pockels effect when a voltage is applied from the power supply 321d.
The Pockels cell 321 a may modulate the phase of the incident pulse laser beam 30 and generate a phase difference (retardation) in the pulse laser beam 30 according to the applied voltage.
When a half-wave voltage is applied from the power supply 321d, the Pockels cell 321a generates a phase difference π with respect to the pulse laser beam 30 which is linearly polarized light in the Y direction transmitted through the polarizer 321b, It may be converted into pulsed laser light 30 which is linearly polarized in the direction.
On the other hand, when no voltage is applied from the power supply 321d, the Pockels cell 321a transmits the pulse laser beam 30 in the Y-direction linearly polarized light transmitted through the polarizer 321b without transmitting the polarization state. It is also good.

The control unit 330 may output a drive signal to the power supply 321 d so that a voltage is applied to the Pockels cell 321 a in synchronization with the timing when the pulse laser light 30 enters the Pockels cell 321 a.
The control unit 330 may output a drive signal to the power supply 321 d such that a voltage having a pulse width that can absorb the time jitter of the pulsed laser light 30 is applied to the Pockels cell 321 a. For example, as shown in FIG. 3B, when the pulse width of the pulsed laser light 30 is about 20 ns, the control unit 330 may output a drive signal such that the pulse width of the applied voltage is about 100 ns.

The pulsed laser light 30 that has entered the first optical switch 321 can enter the polarizer 321 b disposed on the upstream side. The pulse laser beam 30 incident on the polarizer 321 b may transmit the linearly polarized light component in the Y direction and may be incident on the Pockels cell 321 a as the pulse laser beam 30 which is linearly polarized light in the Y direction.

When a voltage is not applied to the Pockels cell 321a, the pulsed laser light 30 in the Y-direction linearly polarized light incident on the Pockels cell 321a passes the Pockels cell 321a as the Y-direction linearly polarized light and is disposed downstream. Can be incident on the polarizer 321c.
In this case, the pulse laser beam 30 which is linearly polarized light in the Y direction that has entered the polarizer 321 c can be reflected by the polarizer 321 c.
As a result, the pulsed laser light 30 in the linearly polarized light in the Y direction that has entered the first optical switch 321 can not pass through the first optical switch 321.

Similarly, when a voltage is not applied to the Pockels cell 321a, light such as return light in linearly polarized light in the X direction incident on the Pockels cell 321a from the downstream side passes through the Pockels cell 321a as linearly polarized light in the X direction Can be incident on the polarizer 321 b disposed on the upstream side.
In this case, light in linear polarization in the X direction that has entered the polarizer 321 b can be reflected by the polarizer 321 b.
In addition, light such as return light that is linearly polarized light in the Y direction that has entered the first optical switch 321 from the downstream side can be reflected by the polarizer 321 c.

On the other hand, when a half-wave voltage is applied to the Pockels cell 321a, the pulsed laser light 30 in linear polarization in the Y direction incident on the Pockels cell 321a is converted into pulsed laser light 30 in linear polarization in the X direction, The light may be incident on the polarizer 321 c disposed downstream.
In this case, the pulse laser beam 30 which is linearly polarized light in the X direction and has entered the polarizer 321 c can pass through the polarizer 321 c.
As a result, the pulse laser beam 30 in linear polarization in the Y direction incident on the first optical switch 321 can be converted into pulse laser beam 30 in linear polarization in the X direction and can pass through the first optical switch 321 .

Thus, the first optical switch 321 can pass the pulse laser beam 30 by applying a voltage to the Pockels cell 321 a in accordance with the incident timing of the pulse laser beam 30. The first optical switch 321 can suppress the passage of return light from the regenerative amplifier 370 or the like disposed downstream of the first optical switch 321. That is, the first optical switch 321 can have the function of an optical isolator.
The second optical switch 322 also operates on the same principle as the first optical switch 321, and may have the function of an optical isolator.
The first and second

optical switches

321 and 322 may be configured using an electro-optical element including a car cell instead of a Pockels cell.
Alternatively, the first and second

optical switches

321 and 322 may be configured using an acousto-optical element or a magneto-optical element instead of the electro-optical element.

[4.4 Regeneration amplifier]
The detailed configuration of the regenerative amplifier 370 will be described with reference to FIG.
FIG. 4 shows a diagram for explaining the detailed configuration of the regenerative amplifier 370. As shown in FIG.
The regenerative amplifier 370 may include the resonator mirror 371, the resonator mirror 372, the third optical switch 373, the fourth optical switch 374, and the amplifier 375, as described above.

The third optical switch 373 may be disposed on the optical path of the pulsed laser light 30 that has passed through the first optical switch 321 and has entered the regenerative amplifier 370.
The third optical switch 373 may be disposed between the resonator mirror 371 and the amplifier 375.
The third optical switch 373 may be configured using an electro-optical element.
The third optical switch 373 may include a Pockels cell 373a, a polarizer 373b, and a power supply (not shown).

The polarizer 373 b may be disposed on the optical path of the pulse laser beam 30 incident on the regenerative amplifier 370.
The polarizer 373 b may be disposed to intersect the optical path axis of the pulse laser beam 30 incident on the regenerative amplifier 370 at an angle of approximately 45 °.
The polarizer 373 b may be disposed on the optical path of the pulsed laser light 30 reciprocated between the resonator mirrors 371 and 372.
The polarizer 373 b may transmit a specific linear polarization component of the pulse laser beam 30 incident on the polarizer 373 b and reflect the other linear polarization components.
As described above, the pulsed laser beam 30 passing through the first optical switch 321 may be the pulsed laser beam 30 in linear polarization in a specific direction. The pulsed laser light 30 incident on the regenerative amplifier 370 may be pulsed laser light 30 in linear polarization in the specific direction.
The polarizer 373 b may reflect the pulse laser beam 30 in linear polarization in the specific direction, which is input to the reproduction amplifier 370, and transmit the pulse laser beam 30 in linear polarization in a direction substantially perpendicular to the specific direction.

The power supply (not shown) included in the third optical switch 373 may be a power supply that applies a voltage to the Pockels cell 373a.
The drive signal to the third optical switch 373 output from the control unit 330 may be input to the power supply. The power supply may apply an applied voltage to the Pockels cell 373a at the voltage value, pulse width, and application timing of the applied voltage specified by the input drive signal.
The other configuration of the power supply may be the same as the power supply 321 d included in the first optical switch 321.

The Pockels cell 373a may be disposed on the optical path of the pulsed laser light 30 reciprocated between the resonator mirrors 371 and 372.
The Pockels cell 373a may be disposed between the resonator mirror 371 and the polarizer 373b.
When a voltage is applied from a power supply (not shown), the Pockels cell 373a generates a phase difference of π / 2 with respect to the linearly polarized pulse laser beam 30 incident thereon and converts it into circularly polarized pulse laser beam 30. It is also good.
When a voltage is applied from a power supply (not shown), the Pockels cell 373a generates a phase difference of π / 2 with respect to the incident circularly polarized pulse laser beam 30 and converts it into linearly polarized pulse laser beam 30. You may
On the other hand, when no voltage is applied from a power supply (not shown), the Pockels cell 321a may transmit the incident linearly polarized pulse laser beam 30 without converting the polarization state.
The other configuration of the Pockels cell 321a may be similar to that of the Pockels cell 321a included in the first optical switch 321.

The fourth optical switch 374 may be disposed on the optical path of the pulsed laser light 30 reciprocated between the resonator mirrors 371 and 372.
The fourth optical switch 374 may be disposed between the resonator mirror 372 and the amplifier 375.
The fourth optical switch 374 may be configured using an electro-optical element.
The fourth light switch 374 may include a Pockels cell 374a, a polarizer 374b, and a power supply (not shown).

The polarizer 374 b may be disposed on the optical path of the pulsed laser light 30 reciprocated between the resonator mirrors 371 and 372.
The polarizer 374 b may be disposed to intersect the optical path axis of the pulsed laser light 30 reciprocated between the resonator mirrors 371 and 372 at an angle of about 45 °.
The polarizer 374b may transmit a specific linear polarization component of the pulsed laser light 30 incident on the polarizer 374b, and reflect the other linear polarization components.
The polarizer 374 b may be arranged in a parallel nicol state with respect to the polarizer 373 b included in the third light switch 373.

The power supply (not shown) included in the fourth optical switch 374 may be a power supply that applies a voltage to the Pockels cell 374a.
The drive signal to the fourth optical switch 374 output from the control unit 330 may be input to the power supply. The power supply may apply an applied voltage to the Pockels cell 374a at the voltage value, pulse width, and application timing of the applied voltage specified by the input drive signal.
The other configuration of the power supply may be the same as the power supply included in the third optical switch 373.

The Pockels cell 374a may be disposed on the optical path of the pulsed laser light 30 reciprocated between the resonator mirrors 371 and 372.
Pockels cell 374a may be disposed between resonator mirror 372 and polarizer 374b.
The other configuration of the Pockels cell 374a may be the same as the Pockels cell 373a included in the third optical switch 373.

The amplifier 375 may be a slab amplifier.
The amplifier 375 may be disposed between the third optical switch 373 and the fourth optical switch 374.
The amplifier 375 may include a housing 375a, a window 375b, a window 375c, a concave mirror 375d, and a concave mirror 375e, in addition to a pair of discharge electrodes not shown.

The inside of the housing 375a may be airtightly filled with CO ₂ gas which is an amplification medium.

Windows

375b and 375c may be disposed on the side surface of the housing 375a.
The

windows

375b and 375c may guide the pulsed laser light 30 incident on the amplifier 375 to the inside of the housing 375a. The

windows

375b and 375c may guide the pulsed laser light 30 output from the amplifier 375 to the outside of the housing 375a.

The pair of discharge electrodes may be disposed inside the housing 375a.
Each of the pair of discharge electrodes may be formed in a substantially plate shape.
Each of the pair of discharge electrodes may be disposed to face each other at a predetermined distance from each other. Each of the pair of discharge electrodes may be arranged to be substantially parallel to the optical path axis of the pulsed laser beam 30 incident on the amplifier 375. In the example of FIG. 4, each of the pair of discharge electrodes may be arranged to be substantially parallel to the paper surface of FIG. 4. A discharge space may be formed between the pair of discharge electrodes.
Each of the pair of discharge electrodes may be cooled by a cooling device (not shown).
One discharge electrode of the pair of discharge electrodes may be grounded, and the other discharge electrode may be connected to the RF power supply 380. A high frequency discharge voltage may be supplied by the RF power supply 380 between the pair of discharge electrodes.
When a discharge voltage is supplied between the pair of discharge electrodes, the CO ₂ gas filling the discharge space formed between the pair of discharge electrodes can be excited. As a result, the pulsed laser light 30 incident on the amplifier 375 can be imparted with energy and amplified when passing through the discharge space.

Each of concave mirrors 375d and 375e may be disposed inside housing 375a.
The concave mirrors 375 d and 375 e may be arranged to sandwich the discharge space formed between the pair of discharge electrodes.
Each of concave mirrors 375d and 375e may be a confocal cylindrical mirror.
Each of concave mirrors 375 d and 375 e may reflect pulse laser light 30 incident on amplifier 375 in multiple passes in multiple passes. Thereby, the pulse laser beam 30 can be multipath amplified in the discharge space formed between the pair of discharge electrodes.
The amplifier 375 may be a three-axis orthogonal amplifier or a high-speed axial-flow amplifier.

The pulsed laser light 30 incident on the regenerative amplifier 370 may be pulsed laser light 30 in linear polarization in a specific direction. The pulse laser beam 30 may be incident on the polarizer 373 b. The pulse laser beam 30 which has entered the polarizer 373 b may be reflected by the polarizer 373 b and may enter the Pockels cell 373 a as it is linearly polarized.
Here, the control unit 330 outputs a drive signal to the power supply of the third optical switch 373 so that a voltage is applied to the Pockels cell 373a in synchronization with the timing when the pulse laser light 30 enters the Pockels cell 373a. It is also good.
When a voltage is applied to the Pockels cell 373a, the linearly polarized pulse laser beam 30 incident on the Pockels cell 373a is converted into the circularly polarized pulse laser beam 30 when passing through the Pockels cell 373a, and the resonator mirror It may be incident on 371. The pulsed laser light 30 incident on the resonator mirror 371 can be reflected by the resonator mirror 371 and enter the Pockels cell 373a again as circularly polarized light.

The circularly polarized pulsed laser light 30 reentered into the Pockels cell 373a may be converted into linearly polarized pulsed laser light 30 when it passes through the Pockels cell 373a again. At this time, the pulse laser beam 30 which has passed through the Pockels cell 373a again can be converted into linearly polarized pulse laser beam 30 having a polarization direction substantially perpendicular to the polarization direction of the pulse laser beam 30 incident on the regenerative amplifier 370. . The linearly polarized pulsed laser light 30 that has again passed through the Pockels cell 373a may enter the polarizer 373b again. The pulsed laser light 30 re-incident on the polarizer 373 b can be transmitted through the polarizer 373 b and incident on the amplifier 375 as linearly polarized light.
Here, the control unit 330 stops the output of the drive signal output to the power supply of the third optical switch 373 so that no voltage is applied to the Pockels cell 373 a after the pulse laser beam 30 passes through the Pockels cell 373 a again. You may

The pulsed laser light 30 incident on the amplifier 375 may be incident on the inside of the housing 375a through the window 375b. The pulsed laser light 30 incident into the housing 375a may be multipath-amplified while being reflected by the concave mirrors 375d and 375e many times in the discharge space formed between the pair of discharge electrodes. The multipass amplified pulsed laser light 30 can be output from the amplifier 375 through the window 375c as it is linearly polarized. The polarization direction of the linearly polarized pulsed laser light 30 output from the amplifier 375 may remain substantially perpendicular to the polarization direction of the pulsed laser light 30 incident on the regenerative amplifier 370.

The pulsed laser light 30 output from the amplifier 375 may be incident on the polarizer 374b. The pulsed laser light 30 incident on the polarizer 374b can be transmitted through the polarizer 374b and incident on the Pockels cell 374a as linearly polarized light.
Here, the control unit 330 prevents a drive signal from being output to the power supply of the fourth optical switch 374 so that a voltage is not applied to the Pockels cell 374a when the pulse laser light 30 enters the Pockels cell 374a. It is also good.
When a voltage is not applied to the Pockels cell 374a, the linearly polarized pulsed laser light 30 entering the Pockels cell 374a can pass through the Pockels cell 374a as it is and enter the resonator mirror 372. The pulsed laser light 30 incident on the resonator mirror 372 may be reflected by the resonator mirror 372 and pass through the Pockels cell 374a as linearly polarized light. The linearly polarized pulsed laser light 30 that has again passed through the Pockels cell 374a may reenter the polarizer 374b. The pulsed laser light 30 re-incident on the polarizer 374 b can pass through the polarizer 374 b and re-enter the amplifier 375 as linearly polarized light.

The pulsed laser light 30 re-incident on the amplifier 375 can be multipath amplified and output again from the amplifier 375 as described above. The polarization direction of the linearly polarized pulsed laser light 30 output again from the amplifier 375 may remain substantially perpendicular to the polarization direction of the pulsed laser light 30 incident on the regenerative amplifier 370.
The pulsed laser light 30 output again from the amplifier 375 can pass through the polarizer 373 b and the Pockels cell 373 a and be reflected by the resonator mirror 371.

While voltage is not applied to the

Pockels cells

373a and 374a, the pulsed laser light 30 passes through the

Pockels cells

373a and 374a and the

polarizers

373b and 374b, and is amplified by the amplifier 375 while being interposed between the resonator mirrors 371 and 372 It can go back and forth.

Thereafter, the control unit 330 drives the power supply of the fourth optical switch 374 so that a voltage is applied to the Pockels cell 374a in synchronization with the timing when the pulse laser light 30 output from the amplifier 375 enters the Pockels cell 374a. A signal may be output.
When a voltage is applied to the Pockels cell 374a, the linearly polarized pulse laser beam 30 incident on the Pockels cell 374a is converted into the circularly polarized pulse laser beam 30 when passing through the Pockels cell 374a, and the resonator mirror It may be incident on 372. The pulsed laser light 30 incident on the resonator mirror 372 may be reflected by the resonator mirror 372 and may enter the Pockels cell 374a again as circularly polarized light.
The circularly polarized pulsed laser light 30 re-incident on the Pockels cell 374a can be converted into linearly polarized pulsed laser light 30 when passing through the Pockels cell 374a again. At this time, the pulsed laser light 30 that has passed through the Pockels cell 374a again can be converted into linearly polarized pulsed laser light 30 having a polarization direction substantially parallel to the polarization direction of the pulsed laser light 30 that has entered the regenerative amplifier 370. The linearly polarized pulsed laser light 30 that has again passed through the Pockels cell 374a may reenter the polarizer 374b. The pulsed laser light 30 re-incident on the polarizer 374 b may be reflected by the polarizer 374 b and output from the regenerative amplifier 370.

In this manner, the reproduction amplifier 370 can amplify the incident pulse laser beam 30 and output it at a specific timing under the control of the control unit 330.
The pulsed laser light 30 amplified and output by the regenerative amplifier 370 may be incident on the second optical switch 322 through the high reflection mirror.

[4.5 Quantum Cascade Laser]
The detailed configurations of the first to fourth QCLs 311 to 314 will be described with reference to FIG.
The internal configuration of each of the first to fourth QCLs 311 to 314 may be substantially the same as each other.
In the description of FIG. 5, the first QCL 311 will be described as an example.
FIG. 5 shows a diagram for explaining the detailed configuration of the first QCL 311. As shown in FIG.

The first QCL 311 may be a distributed feedback quantum cascade laser.
The first QCL 311 may include a semiconductor element 3111 and a Peltier element 3112.

The semiconductor element 3111 may be a semiconductor element that generates light using electronic transition between subbands in the quantum well structure.
The semiconductor element 3111 may include an active layer 3111 a, a semiconductor layer 3111 b, and a semiconductor layer 3111 c.
The semiconductor element 3111 may have a stacked structure in which a semiconductor layer 3111 b, an active layer 3111 a, and a semiconductor layer 3111 c are stacked in this order.

The active layer 3111a may have a function of generating and amplifying light.
The active layer 3111a may have a cascade structure in which quantum well layers used for light generation and injection layers that inject electrons into the quantum well layers are alternately stacked.

The semiconductor layers 3111 b and 3111 c may be provided so as to sandwich the active layer 3111 a from both sides in the stacking direction of the semiconductor element 3111.
The semiconductor layers 3111 b and 3111 c may include a guide layer for guiding the light generated in the active layer 3111 a, a cladding layer for confining the light, and the like.
In the vicinity of the active layer 3111 a of the semiconductor layer 3111 b, a grating 3111 d in which a large number of grooves are formed at a predetermined groove interval A may be provided.

The grating 3111 d can function as an optical resonator that selectively returns light in the vicinity of a specific wavelength according to the predetermined groove spacing A. When the gain exceeds the threshold value, the feedback light amount rapidly increases, and light near the specific wavelength can be output as laser light from one end or both ends of the active layer 3111a.
A part of the grooves constituting the grating 3111 d may be formed at an interval other than the predetermined groove interval A. The grooves formed at intervals other than the predetermined groove interval A may be formed at one or more predetermined locations in the output direction of the pulse laser beam. Generally, a distributed feedback laser can emit pulsed laser light of two wavelengths ideally when the grooves of the grating are formed at uniform intervals. On the other hand, when a part of the grooves of the grating 3111 d is formed at an interval other than the predetermined groove interval A, the first QCL 311 can oscillate pulsed laser light of a single wavelength.

The semiconductor layers 3111 b and 3111 c may be provided with a pair of electrode layers (not shown) so as to be sandwiched from both sides in the stacking direction of the semiconductor element 3111.
The pair of electrode layers may be connected to the control unit 330 via a current controller (not shown). An excitation current corresponding to the trigger signal output from the control unit 330 may be supplied from the current controller to the pair of electrode layers. Thus, an excitation current corresponding to the trigger signal can flow through the semiconductor layers 3111 b and 3111 c and the active layer 3111 a sandwiched by the pair of electrode layers.

The Peltier device 3112 may be a device for cooling the semiconductor device 3111.
The Peltier device 3112 may be connected to the control unit 330. The Peltier device 3112 may cool the semiconductor device 3111 under the control of the control unit 330.

When a trigger signal is input to the first QCL 311 from the control unit 330, an excitation current may flow through the active layer 3111a of the first QCL 311.
When an excitation current flows through the active layer 3111a, the active layer 3111a can generate light. The generated light can be resonated while being wavelength-selected by the grating 3111 d and amplified each time it passes through the active layer 3111 a. Then, the light can be output from the end face of the semiconductor element 3111 as pulsed laser light.
Thus, the first QCL 311 can output pulsed laser light under the control of the control unit 330. The oscillation wavelength of the first QCL 311 may depend on the optical path length of the optical resonator in the semiconductor element 3111 and the selected wavelength of the grating 3111 d.
Each of the second to fourth QCLs 312 to 314 can operate on the same principle as that of the first QCL 311 and output pulsed laser light.

The wavelength chirping of the first to fourth QCLs 311 to 314 will be described with reference to FIG.
Wavelength chirping may occur in each of the first through fourth QCLs 311-314 as well.
In the description of FIG. 6, the first QCL 311 will be described as an example.
FIG. 6 shows a diagram for explaining wavelength chirping generated in the first QCL 311. As shown in FIG.

When excitation current is supplied to the first QCL 311 and laser oscillation is performed, heat generation of the semiconductor element 3111 included in the first QCL 311 may increase the temperature of the active layer 3111 a of the semiconductor element 3111 as illustrated in FIG.
When the temperature of the active layer 3111a changes, the refractive index of the active layer 3111a may change. Furthermore, when the temperature of the active layer 3111 a changes, the optical path length of the optical resonator in the semiconductor element 3111 and the interval A of the grooves of the grating 3111 d may change.
Thereby, the oscillation wavelength of the first QCL 311 may change as shown in FIG.

The semiconductor element 3111 of the first QCL 311 may be cooled by the Peltier element 3112. Therefore, the temperature of the active layer 3111a can be permanently kept substantially constant by the heat balance between the heat generation of the semiconductor element 3111 and the cooling of the Peltier element 3112.
However, the temperature of the active layer 3111a may transiently change as follows.
That is, as shown in FIG. 6, the temperature of the active layer 3111a may rise sharply immediately after the excitation current is supplied to the first QCL 311, and may gradually rise with the passage of time. Then, the temperature of the active layer 3111a may drop sharply immediately after the supply of the excitation current is stopped, and may gradually drop with time.
At this time, as the temperature of the active layer 3111a rises, the refractive index of the active layer 3111a may increase and the optical path length of the optical resonator in the semiconductor element 3111 may increase, and the oscillation wavelength of the first QCL 311 may also become long. .
Such a phenomenon in which the oscillation wavelength of a semiconductor laser including QCL changes is called wavelength chirping.
The wavelength of pulsed laser light output from the first QCL 311 can be changed by wavelength chirping.

On the other hand, the wavelength region of the pulse laser beam 30 that can be amplified by the regenerative amplifier 370 and the first to fourth amplifiers 351 to 354 may be determined in advance by the amplification medium of these amplifiers.
For this reason, the pulsed laser light output from the first QCL 311 can be appropriately amplified only when it has a wavelength in a wavelength region that can be amplified by these amplifiers.
When the oscillation wavelength of the first QCL 311 changes due to wavelength chirping, the pulsed laser light output from the first QCL 311 can be appropriately amplified only at the timing when the wavelength of the pulsed laser light reaches the wavelength region that can be amplified. In other words, only the pulse laser beam output from the first QCL 311 can be appropriately amplified at the timing when the wavelength of the pulse laser beam to be output reaches the amplification wavelength region.
That is, a time lag may occur from the timing when the excitation current is supplied to the first QCL 311 to the timing when the wavelength of the output pulse laser light reaches the amplification wavelength region. That is, a time lag may occur from the timing when the trigger signal is output to the first QCL 311 to the timing when the pulse laser light having the wavelength of the amplification wavelength region is output from the first QCL 311.
In the present disclosure, the time lag from the timing when the trigger signal is output to QCL to the timing when the pulse laser light having the wavelength of the amplification wavelength region is output from QCL is also referred to as “emission delay time of QCL”.

The wavelength of pulsed laser light output from each of the second to fourth QCLs 312 to 314 can also be changed by wavelength chirping, as in the first QCL 311.
Then, in each of the second to fourth QCLs 312 to 314, similarly to the first QCL 311, a light emission delay time may occur.

The light emission delay time of each of the first to fourth QCLs 311 to 314 can also vary depending on the load state of each of the first to fourth QCLs 311 to 314.
For example, the behavior of the first QCL 311 in a high load state such as 100 kHz is compared with the behavior of the first QCL 311 in a low load state such as 20 kHz. In FIG. 6, the active layer temperature etc. in the high load state first QCL 311 is shown by a solid line, and the active layer temperature etc. in the low load state first QCL 311 is shown by a broken line.

In the high load state first QCL 311 oscillating at a high repetition frequency, the number of times the excitation current is supplied per unit time may be increased as compared to the low load state first QCL 311 oscillating at a low repetition frequency.
Therefore, the temperature of the active layer 3111a in the first QCL 311 may be higher in the high load state oscillating at a high repetition frequency than in the low load state oscillating at a low repetition frequency.
Along with this, the oscillation wavelength immediately after the excitation current is supplied to the first QCL 311 may be shifted to the longer wavelength side in the high load state than in the low load state. Furthermore, the fluctuation range of the oscillation wavelength due to wavelength chirping in the first QCL 311 may be larger in the high load state than in the low load state.
As a result, the light emission delay time of the first QCL 311 may be shorter in the high load state than in the low load state.
That is, in the first QCL 311, the timing when the pulse laser light having the wavelength of the amplification wavelength region is output may be earlier in the high load state than in the low load state.
In each of the second to fourth QCLs 312 to 314 as well as the first QCL 311, the timing when the pulse laser light having the wavelength in the amplification wavelength region is output may be earlier in the high load state than in the low load state.
Thus, the timing at which the pulsed laser light having the wavelength in the amplification wavelength region is output from each of the first to fourth QCLs 311 to 314 may vary depending on the load state of each QCL.
The delay times Dq1 to D4 added to the trigger signal have substantially the same pulse laser beams 30 having wavelengths in the amplification wavelength region, taking into consideration the light emission delay times of the first to fourth QCLs 311 to 314, respectively. It is predetermined to be output at timing.

[5. Task]
In the laser device 3, the timing when the pulsed laser light in the amplification wavelength region is output from each of the first to fourth QCLs 311 to 314, and the first to fourth

optical switches

321, 322, 373 and 374 are driven. The timing may need to be synchronized.
However, when the operating condition of the laser device 3 is changed, the timing of the two may not be synchronized.

For example, the repetition frequency of the pulse laser beam 31 output from the laser device 3 may be changed to a low value by an instruction from the exposure device 6 or the like. In this case, the load states of the first to fourth QCLs 311 to 314 may be lowered, and the timings at which pulse laser beams having wavelengths in the amplification wavelength region are output from the first to fourth QCLs 311 to 314 may be delayed.
Thereby, the timing when pulse laser light having the wavelength of the amplification wavelength region is output from each of the first to fourth QCLs 311 to 314, the timing when the first to fourth

optical switches

321, 322, 373 and 374 are driven, and Can get out of sync.
As a result, the pulsed laser light output from any of the first to fourth QCLs 311 to 314 may not be properly amplified. Also, the pulse laser beam 30 may not pass through any of the first to fourth

optical switches

321, 322, 373 and 374.

Therefore, even when the operating condition of the laser device 3 is changed, a technique capable of appropriately amplifying the pulse laser beam 30 and outputting the pulse laser beam 31 having desired characteristics at a desired timing is required. There is.
It is also conceivable to change, for example, the cooling operation of the Peltier element 3112 according to the change of the operating condition of the laser device 3. However, it is difficult to suppress the transient temperature change of the active layer 3111a only by changing the cooling operation of the Peltier element 3112, and it may be difficult to cope with the wavelength chirping.

[6. EUV light generation system including the laser device of the first embodiment]
[6.1 Configuration]
The EUV light generation system 11 including the laser device 3 of the first embodiment will be described using FIGS. 7 and 8.
FIG. 7 shows the configuration of an EUV light generation system 11 including the laser device 3 of the first embodiment.
In the EUV light generation system 11 including the laser device 3 of the first embodiment, the configurations of the EUV light generation controller 5 and the controller 330 may be different from the EUV light generation system 11 shown in FIG.
In the configuration of the EUV light generation system 11 including the laser device 3 of the first embodiment, the description of the same configuration as that of the EUV light generation system 11 shown in FIG. 2 will be omitted.

The EUV light generation controller 5 of FIG. 7 may include a master trigger generator 51.
The master trigger generation unit 51 may determine the target repetition frequency of the droplets 271 as the master repetition frequency regardless of the target repetition frequency of the EUV light 252 included in the EUV light output command signal.
The master repetition frequency may be a constant repetition frequency predetermined based on the specifications of the EUV light generation apparatus 1, the laser apparatus 3, or the exposure apparatus 6.
The master repetition frequency may be a repetition frequency of an upper limit value that can be taken by the target repetition frequency of the EUV light 252 included in the EUV light output command signal.
The master repetition frequency may be a value that is an integral multiple of the target repetition frequency of the EUV light 252. For example, the master repetition frequency may be 100 kHz, and the target repetition frequency of the EUV light 252 may be 100 Hz, 50 kHz, 33.3 kHz, 25 kHz, 20 kHz, 10 kHz, 1 kHz, or the like.

The EUV light generation controller 5 may generate a target supply signal with the master repetition frequency determined by the master trigger generation unit 51 as the target repetition frequency of the droplets 271.
The EUV light generation controller 5 may output the generated target supply signal to the target supply unit 26 at the master repetition frequency.
The target supply unit 26 can generate and output the droplets 271 at the master repetition frequency. The target sensor 4 can detect the droplets 271 output at the master repetition frequency and output a droplet detection signal to the EUV light generation controller 5.
A droplet detection signal reflecting the master repetition frequency can be input to the EUV light generation controller 5.

The EUV light generation controller 5 may generate a laser output signal based on the droplet detection signal reflecting the master repetition frequency and may output the laser output signal to the controller 330.
Specifically, the EUV light generation controller 5 controls the laser output signal for each pulse in synchronization with the timing when the droplet detection signal of the droplet 271 output at the master repetition frequency is input. It may be output to
The controller 330 may receive a laser output signal reflecting the master repetition frequency.

The EUV light generation controller 5 may separately output various target values such as the target pulse energy of the pulse laser light 31 to the controller 330 without including it in the laser output signal.
In this case, the EUV light generation controller 5 may output the droplet detection signal of the droplet 271 output at the master repetition frequency as it is to the controller 330 as a laser output signal. The EUV light generation controller 5 may output various target values such as the target pulse energy of the pulsed laser light 31 to the controller 330 before outputting the laser output signal. The control unit 330 sets each of the set value of the excitation current included in the trigger signal, the set value of the discharge voltage included in the voltage set signal, and the set value of the discharge current included in the current set signal before the input of the laser output signal. It may be determined in advance.

Further, the EUV light generation controller 5 may generate a division setting signal and output it to the controller 330.
The EUV light generation controller 5 may output a division setting signal to the controller 330 before outputting the laser output signal.
The division setting signal may be a control signal for setting, in the control unit 330, a division ratio when dividing the master repetition frequency.
The division ratio may be a value obtained by dividing the value of the master repetition frequency by the value of the target repetition frequency of the EUV light 252 included in the EUV light output command signal.

The control unit 330 of FIG. 7 may include a divider 331.
The frequency divider 331 may divide the laser output signal output from the EUV light generation controller 5 based on the division setting signal output from the EUV light generation controller 5.
The frequency divider 331 may divide the laser output signal input at a repetition frequency that is substantially the same value as the master repetition frequency using the division ratio included in the division setting signal. The repetition frequency of the divided laser output signal may be a repetition frequency having substantially the same value as the target repetition frequency of the EUV light 252 included in the EUV light output command signal. The repetition frequency of the undivided laser output signal may be a repetition frequency of substantially the same value as the master repetition frequency.

The control unit 330 outputs a drive signal to the optical switch, a voltage setting signal to the RF power supply 380, and a current setting signal to the first to fourth RF power supplies 361 to 364 based on the divided laser output signal. May be
The control unit 330 synchronizes with the timing when the laser output signal is input, and at a repetition frequency of substantially the same value as the target repetition frequency of the EUV light 252, the drive signal to the optical switch, the voltage setting signal, and A current setting signal may be output. The control unit 330 may directly output each of the drive signal to the optical switch, the voltage setting signal, and the current setting signal from the divider 331.
Each of the first and second

optical switches

321 and 322 is incident at a repetition frequency substantially the same as the target repetition frequency of the EUV light 252 in synchronization with the timing when the laser output signal is input to the control unit 330. The pulsed laser light 30 can be passed. Each of the third and fourth

optical switches

373 and 374 is incident at a repetition frequency substantially the same as the target repetition frequency of the EUV light 252 in synchronization with the timing when the laser output signal is input to the control unit 330. The optical path of the pulsed laser light 30 can be changed.
The amplifier 375 of the regenerative amplifier 370 amplifies the pulse laser beam 30 at a repetition frequency substantially the same as the target repetition frequency of the EUV light 252 in synchronization with the timing when the laser output signal is input to the control unit 330. It can be output. Each of the first to fourth amplifiers 351 to 354 synchronizes with the timing when the laser output signal is input to the control unit 330, and generates pulsed laser light at a repetition frequency substantially the same as the target repetition frequency of the EUV light 252. 30 can be amplified and output.

Further, the control unit 330 may output a trigger signal to each of the first to fourth QCLs 311 to 314 based on the laser output signal not divided.
The control unit 330 may output the trigger signal at a repetition frequency substantially the same as the master repetition frequency in synchronization with the timing when the laser output signal is input.
At this time, the control unit 330 may output the trigger signal at a timing delayed by a predetermined delay time Dq1 to 4 from the timing when the laser output signal is input.
Each of the first to fourth QCLs 311 to 314 can output pulse laser light at a repetition frequency substantially the same as the master repetition frequency in synchronization with the timing when the laser output signal is input to the control unit 330.

The other configuration of the EUV light generation system 11 including the laser device 3 of the first embodiment may be the same as that of the EUV light generation system 11 shown in FIG.

[6.2 Operation]
FIG. 8 is a diagram for explaining the operation related to the laser oscillation of the EUV light generation system 11 including the laser device 3 of the first embodiment.
In the operation of the EUV light generation system 11 including the laser device 3 of the first embodiment, the description of the same operation as that of the EUV light generation system 11 shown in FIG. 2 will be omitted.

An EUV light output command signal may be transmitted from the exposure apparatus control unit 61 to the EUV light generation control unit 5.
The EUV light generation controller 5 sends various target values such as target pulse energy of the pulse laser beam 31 to the controller 330 based on various target values such as target pulse energy of the EUV light 252 included in the EUV light output command signal. You may output it.
The control unit 330 determines the set values of the excitation current to be set in the first to fourth QCLs 311 to 314 based on various target values such as the target pulse energy of the pulsed laser light 31 output from the EUV light generation controller 5 You may
The control unit 330 may determine the set value of the discharge voltage included in the voltage setting signal output to the RF power supply 380 based on various target values such as the target pulse energy of the pulse laser light 31.
The control unit 330 determines the set value of the discharge current included in the current setting signal output to the first to fourth RF power supplies 361 to 364 based on various target values such as the target pulse energy of the pulse laser light 31. May be

The EUV light generation controller 5 may generate a division setting signal using the target repetition frequency of the EUV light 252 and the master repetition frequency included in the EUV light output command signal, and may output the generated division setting signal to the controller 330.
The target repetition frequency of the EUV light 252 may be, for example, 50 kHz. The master repetition frequency may be, for example, 100 kHz. In this example, the division ratio included in the division setting signal may be two.

The EUV light generation controller 5 may generate a target supply signal having the target repetition frequency of the droplets 271 as a master repetition frequency, and may output the target supply signal to the target supply unit 26.
The target supply unit 26 may generate droplets 271 at the master repetition frequency and output them into the chamber 2. The target sensor 4 can output the droplet detection signal of the droplets 271 output at the master repetition frequency to the EUV light generation controller 5.
The EUV light generation controller 5 may output the droplet detection signal reflecting the master repetition frequency as it is to the controller 330 as a laser output signal.

The control unit 330 may determine the delay times Dq1 to D4 to be added to the trigger signal based on the laser output signal not divided.
The control unit 330 may divide the laser output signal based on the division setting signal.
The control unit 330 may determine the delay times Dp1 to D4 to be added to the drive signal to the optical switch based on the divided laser output signal.

The controller 330 controls the first to fourth QCLs 311 at a timing delayed by a delay time Dq1 to 4 from the timing when the laser output signal which is not divided is input, and the trigger signal including the preset setting value of the excitation current. It may be output to each of 314 314.
Each of the first to fourth QCLs 311 to 314 can output pulsed laser light based on the input trigger signal.
At this time, each of the first to fourth QCLs 311 to 314 is a pulse laser beam 30 having a wavelength of an amplification wavelength region at a repetition frequency reflecting a master repetition frequency having a value that is an integral multiple of the target repetition frequency of the EUV light 252. Can be output.
The optical path adjuster 315 may superimpose the optical paths of the pulsed laser light output from the first to fourth QCLs 311 to 314 substantially on one optical path, and may output the optical path as the pulsed laser light 30 to the first optical switch 321. .

The control unit 330 may output a voltage setting signal including a preset discharge voltage setting value to the RF power supply 380 in synchronization with the timing when the divided laser output signal is input.
The RF power supply 380 may supply a discharge voltage to the discharge electrode of the amplifier 375 of the regenerative amplifier 370 based on the input voltage setting signal.
The control unit 330 outputs the current setting signal including the preset setting value of the discharge current to the first to fourth RF power supplies 361 to 364 in synchronization with the timing when the divided laser output signal is input. May be
The first to fourth RF power supplies 361 to 364 may supply a discharge current to the discharge electrodes of the first to fourth amplifiers 351 to 354, based on the input current setting signal.

The control unit 330 may output the drive signal to the first optical switch 321 to the first optical switch 321 at a timing delayed by the delay time Dp1 from the timing when the divided laser output signal is input.
The first optical switch 321 can selectively pass the incident pulse laser beam 30 based on the input drive signal, and can output it to the regenerative amplifier 370.
At this time, the repetition frequency of the pulsed laser light 30 passing through the first optical switch 321 may be substantially equal to the target repetition frequency of the EUV light 252. That is, the first optical switch 321 can pass the pulse laser beam 30 having the wavelength of the amplification wavelength region at a repetition frequency reflecting the target repetition frequency of the EUV light 252.
The pulsed laser light 30 that has not passed through the first optical switch 321 may be reflected by the polarizer 321 c of FIG. 3 and absorbed by a beam damper (not shown).

The control unit 330 may output the drive signal to the third optical switch 373 to the third optical switch 373 at a timing delayed by the delay time Dp3 from the timing when the divided laser output signal is input.
The third optical switch 373 can change the optical path of the incident pulse laser beam 30 based on the input drive signal, and introduce the pulse laser beam 30 into the regenerative amplifier 370.
At this time, the pulsed laser light 30 introduced into the regenerative amplifier 370 may be only the pulsed laser light 30 selectively passed by the first optical switch 321. That is, the third optical switch 373 can introduce the pulsed laser light 30 having the wavelength of the amplification wavelength region into the regenerative amplifier 370 at a repetition frequency reflecting the target repetition frequency of the EUV light 252.
The pulsed laser light 30 introduced into the regenerative amplifier 370 can be amplified each time it passes through the amplifier 375 while reciprocating between the resonator mirrors 371 and 372.

The control unit 330 may output the drive signal to the fourth optical switch 374 to the fourth optical switch 374 at a timing delayed by the delay time Dp4 from the timing when the divided laser output signal is input.
The fourth optical switch 374 can change the optical path of the incident pulse laser beam 30 based on the input drive signal, and can output it from the regenerative amplifier 370 to the high reflection mirror.
At this time, the fourth optical switch 374 outputs the pulse laser beam 30 having a wavelength in the amplification wavelength region and appropriately amplified from the regenerative amplifier 370 at a repetition frequency reflecting the target repetition frequency of the EUV light 252. obtain.
The high reflection mirror can reflect the incident pulse laser beam 30 and output it to the second optical switch 322.

The control unit 330 may output the drive signal to the second optical switch 322 to the second optical switch 322 at a timing delayed by the delay time Dp2 from the timing when the divided laser output signal is input.
The second optical switch 322 can pass the incident pulse laser beam 30 based on the input drive signal, and can output it to the first to fourth amplifiers 351 to 354.
At this time, the second optical switch 322 can pass the appropriately amplified pulsed laser light 30 having the wavelength of the amplification wavelength region at a repetition frequency reflecting the target repetition frequency of the EUV light 252.
Each of the first to fourth amplifiers 351 to 354 can appropriately amplify the pulse laser beam 30 in order.
The pulsed laser light 30 amplified by the fourth amplifier 354 at the final stage can be output to the outside of the laser apparatus 3 as the pulsed laser light 31 at a repetition frequency reflecting the target repetition frequency of the EUV light 252.

The other operation of the EUV light generation system 11 including the laser device 3 of the first embodiment may be the same as that of the EUV light generation system 11 shown in FIG.

[6.3 Action]
As described above, the control unit 330 causes the first to fourth QCLs 311 to 314 to generate trigger signals at repetition frequencies reflecting the master repetition frequency regardless of the target repetition frequency of the EUV light 252 requested from the exposure apparatus control unit 61. It can be output.
Therefore, the load state of each of the first to fourth QCLs 311 to 314 can be substantially constant without largely fluctuating even if the target repetition frequency of the EUV light 252 is changed by a request from the exposure apparatus control unit 61.
Thus, each of the first to fourth QCLs 311 to 314 can output pulsed laser light having a wavelength of an amplification wavelength region at substantially the same timing regardless of the target repetition frequency of the EUV light 252.
On the other hand, each of the first and second

optical switches

321 and 322 can pass the pulse laser beam 30 having the wavelength of the amplification wavelength region at a repetition frequency reflecting the target repetition frequency of the EUV light 252. Each of the third and fourth

optical switches

373 and 374 can change the optical path of the pulsed laser light 30 having the wavelength of the amplification wavelength region at a repetition frequency reflecting the target repetition frequency of the EUV light 252. Each of the regenerative amplifier 370 and the first to fourth amplifiers 351 to 354 can appropriately amplify and output the pulse laser beam 30 at a repetition frequency reflecting the target repetition frequency of the EUV light 252.
Thus, when the target repetition frequency of the EUV light 252 is changed, the laser device 3 of the first embodiment can output the pulse laser light 31 at a repetition frequency reflecting the target repetition frequency of the EUV light 252. In addition, the laser apparatus 3 according to the first embodiment is a pulse laser appropriately amplified while suppressing fluctuations in the load states of the first to fourth QCLs 311 to 314 even if the target repetition frequency of the EUV light 252 is changed. Light 31 can be output.
Therefore, the laser device 3 according to the first embodiment appropriately amplifies the pulsed laser beam 30 even when the operating condition is changed, and outputs the pulsed laser beam 31 having desired characteristics at a desired timing. It can.

[7. EUV light generation system including the laser device of the second embodiment]
The EUV light generation system 11 including the laser device 3 of the second embodiment will be described using FIGS. 9 to 11.
FIG. 9 shows the configuration of an EUV light generation system 11 including the laser device 3 of the second embodiment.
In the EUV light generation system 11 including the laser device 3 of the second embodiment, when the target repetition frequency of the EUV light 252 is changed in response to a request from the exposure apparatus control unit 61, the target repetition frequency of the droplets 271 is accordingly May be changed.
In this case, in the EUV light generation system 11 according to the second embodiment, the repetition frequency of the droplet detection signal of the droplets 271 output according to the target repetition frequency of the droplets 271 may be changed. Then, the repetition frequency of the trigger signal output based on the droplet detection signal may also be changed. Thereby, the load state of each of the first to fourth QCLs 311 to 314 may change.
Therefore, the EUV light generation system 11 according to the second embodiment may cope with wavelength chirping by adjusting the delay times Dq1 to D4 added to the trigger signal.

The EUV light generation system 11 according to the second embodiment may be different from the EUV light generation system 11 according to the first embodiment shown in FIG. 7 in the configurations of the EUV light generation controller 5 and the controller 330.
The EUV light generation controller 5 according to the second embodiment may not include the master trigger generator 51, and may not output the division setting signal to the controller 330.
The control unit 330 according to the second embodiment may not include the divider 331.
In the configuration and operation of the EUV light generation system 11 according to the second embodiment, the description of the same configuration and operation as the EUV light generation system 11 according to the first embodiment shown in FIGS. 7 and 8 will be omitted.

The EUV light generation controller 5 of FIG. 9 may determine the target repetition frequency of the droplets 271 to be the same value as the target repetition frequency of the EUV light 252 included in the EUV light output command signal instead of the master repetition frequency. .
The EUV light generation controller 5 may generate a target supply signal with the same value as the target repetition frequency of the EUV light 252 as the target repetition frequency of the droplets 271.
The EUV light generation controller 5 may output the generated target supply signal to the target supplier 26 at the same repetition frequency as the target repetition frequency of the EUV light 252.
The target supply unit 26 may generate and output the droplets 271 at the same repetition frequency as the target repetition frequency of the EUV light 252. The target sensor 4 can detect the droplets 271 output at the same repetition frequency as the target repetition frequency of the EUV light 252, and can output a droplet detection signal to the EUV light generation controller 5.
The EUV light generation controller 5 may receive a droplet detection signal reflecting the target repetition frequency of the EUV light 252 included in the EUV light output command signal.

The EUV light generation controller 5 may generate a laser output signal based on the droplet detection signal reflecting the target repetition frequency of the EUV light 252 included in the EUV light output command signal, and may output it to the controller 330.
Specifically, the EUV light generation controller 5 synchronizes with the timing when the droplet detection signal of the droplet 271 output at the same repetition frequency as the target repetition frequency of the EUV light 252 is input, May be output to the control unit 330 for each pulse.
The control unit 330 may receive a laser output signal that reflects the target repetition frequency of the EUV light 252 included in the EUV light output command signal.

The control unit 330 of FIG. 9 synchronizes with the timing when the laser output signal is input, the drive signal to the optical switch, the voltage setting signal to the RF power supply 380, and the first at the target repetition frequency of the EUV light 252. The current setting signal to the fourth RF power supplies 361 to 364 may be output.
Each of the first and second

optical switches

321 and 322 is a pulse laser that is incident at a repetition frequency reflecting the target repetition frequency of the EUV light 252 in synchronization with the timing when the laser output signal is input to the control unit 330. The light 30 can be passed. Each of the third and fourth

optical switches

373 and 374 is a pulse laser that is incident at a repetition frequency reflecting the target repetition frequency of the EUV light 252 in synchronization with the timing when the laser output signal is input to the control unit 330. The light path of light 30 may be changed.
The amplifier 375 of the regenerative amplifier 370 amplifies and outputs the pulse laser beam 30 at a repetition frequency reflecting the target repetition frequency of the EUV light 252 in synchronization with the timing when the laser output signal is input to the control unit 330. obtain. Each of the first to fourth amplifiers 351 to 354 synchronizes with the timing when the laser output signal is input to the control unit 330, and the pulse laser beam 30 is emitted at a repetition frequency reflecting the target repetition frequency of the EUV light 252. It can be amplified and output.

Further, the control unit 330 outputs a trigger signal to each of the first to fourth QCLs 311 to 314 at a repetition frequency reflecting the target repetition frequency of the EUV light 252 in synchronization with the timing when the laser output signal is input. May be
At this time, the control unit 330 may output the trigger signal at a timing delayed by a predetermined delay time Dq1 ′ to 4 ′ from the timing when the laser output signal is input.
The delay time Dq1 ′ to 4 ′ added to the trigger signal may be a value adjusted from the delay time Dq1 to 4 according to the change in the load state of each of the first to fourth QCLs 311 to 314. .
The length of each of the delay times Dq1 'to 4' is such that even if the load condition of each of the first to fourth QCLs 311 to 314 changes, pulsed laser beams having wavelengths in the amplification wavelength region are output at substantially the same timing It may be defined as
The control unit 330 may include a storage operation unit 332 that calculates delay times Dq1 ′ to 4 ′ added to the trigger signal.

The delay times Dq1 ′ to 4 ′ added to the trigger signal will be described with reference to FIGS. 10 and 11.
FIG. 10 is a diagram for explaining the delay times Dq1 ′ to 4 ′ added to the trigger signal output from the control unit 330 included in the laser apparatus 3 of the second embodiment. FIG. 11 shows the result of measuring the relationship between the light emission delay time of QCL and the repetition frequency.

As described above, in the laser device 3 of the second embodiment, each of the first to fourth QCLs 311 to 314 is pulsed at a repetition frequency reflecting the target repetition frequency of the EUV light 252 included in the EUV light output command signal. Laser light may be output.
That is, in the laser device 3 of the second embodiment, when the target repetition frequency of the EUV light 252 is changed, the repetition frequency of the trigger signal may also be changed, so the load states of the first to fourth QCLs 311 to 314 change. It can.
In this case, as shown in the upper part of FIG. 10, the timing at which the pulse laser light having the wavelength of the amplification wavelength region is output from each of the first to fourth QCLs 311 to 314 may vary. That is, the light emission delay time may occur in each of the first to fourth QCLs 311 to 314.
In particular, the light emission delay time of each of the first to fourth QCLs 311 to 314 may vary according to the repetition frequency of each of the first to fourth QCLs 311 to 314, as shown in FIG.
FIG. 11 shows how the light emission delay time of each of the first to fourth QCLs 311 to 314 changes when the repetition frequency of each of the first to fourth QCLs 311 to 314 is changed based on 100 Hz. It is shown.
Furthermore, the variation of the light emission delay time of each of the first to fourth QCLs 311 to 314 may be different for each of the first to fourth QCLs 311 to 314, as is apparent from the different slopes of the graphs in FIG.

Therefore, the storage operation unit 332 of the control unit 330 may store in advance the measurement result regarding the relationship between the light emission delay time of the QCL and the repetition frequency illustrated in FIG.
When the target repetition frequency of the EUV light 252 is changed, the storage operation unit 332 performs the following processing based on the measurement result on the relationship between the light emission delay time of the QCL and the repetition frequency shown in FIG. May be Thereby, the storage operation unit 332 may calculate the delay times Dq1 ′ to 4 ′ added to the trigger signal.

That is, the memory operation unit 332 refers to the measurement result regarding the relationship between the light emission delay time of QCL and the repetition frequency in FIG. 11 and determines the first to fourth QCLs 311 to 314 according to the target repetition frequency of the EUV light 252. The amount of fluctuation of the light emission delay time may be specified.
Under the present circumstances, when the value of the light emission delay time is not published in the said measurement result of FIG. 11, the memory | storage calculating part 332 is based on the said measurement result of FIG. May be derived. The correlation equation may be described by a linear approximation function, a polynomial approximation function, or a high-order approximation function. Then, the storage operation unit 332 may calculate the variation of the light emission delay time of each of the first to fourth QCLs 311 to 314 using the derived correlation equation.
Subsequently, the storage operation unit 332 subtracts the fluctuation amount of the specified light emission delay time from the delay times Dq1 to D4 added to the trigger signal before the target repetition frequency of the EUV light 252 is changed. The times Dq1 ′ to 4 ′ may be calculated.

The control unit 330 may determine the value obtained by the storage operation unit 332 as new delay time Dq1 ′ to 4 ′ to be added to the trigger signal.
Then, as shown in the lower part of FIG. 10, the control unit 330 performs the first to fourth QCLs 311 to 314 at timings delayed by delay times Dq1 ′ to 4 ′ newly determined from the timing when the laser output signal is input. A trigger signal may be output to each of
Thereby, each of the first to fourth QCLs 311 to 314 synchronizes with the timing when the laser output signal is input to the control unit 330, and generates pulse laser light at a repetition frequency reflecting the target repetition frequency of the EUV light 252. It can be output. In addition, each of the first to fourth QCLs 311 to 314 can output pulsed laser light having a wavelength in the amplification wavelength region at substantially the same timing even if the load state is changed.

The other configuration and operation of the EUV light generation system 11 including the laser device 3 of the second embodiment are the same as the EUV light generation system 11 including the laser device 3 of the first embodiment shown in FIGS. 7 and 8. It may be

As described above, the control unit 330 adjusts the delay times Dq1 to Dq1 ′ to Dq1 ′ to 4 ′ based on the target repetition frequency of the EUV light 252 requested from the exposure apparatus control unit 61, and performs the first to fourth QCLs 311 to A trigger signal may be output to each of 314.
Therefore, even if the target repetition frequency of the EUV light 252 is changed due to the request from the exposure apparatus control unit 61 and the load state changes, each of the first to fourth QCLs 311 to 314 has amplified wavelength regions at substantially the same timing. Pulse laser light having a wavelength of
On the other hand, each of the first and second

optical switches

373 and 374 can change the optical path of the pulsed laser light 30 having the wavelength of the amplification wavelength region at a repetition frequency reflecting the target repetition frequency of the EUV light 252. Each of the regenerative amplifier 370 and the first to fourth amplifiers 351 to 354 can appropriately amplify and output the pulse laser beam 30 at a repetition frequency reflecting the target repetition frequency of the EUV light 252.
Thus, when the target repetition frequency of the EUV light 252 is changed, the laser device 3 of the second embodiment can output the pulse laser light 31 at a repetition frequency reflecting the target repetition frequency of the EUV light 252. In addition, the laser device 3 according to the second embodiment is a pulse laser appropriately amplified while coping with fluctuations in the load states of the first to fourth QCLs 311 to 314 even if the target repetition frequency of the EUV light 252 is changed. Light 31 can be output.
Therefore, the laser device 3 according to the second embodiment appropriately amplifies the pulsed laser beam 30 even when the operating conditions are changed, and outputs the pulsed laser beam 31 having desired characteristics at a desired timing. It can.

[8. EUV light generation system including the laser device of the third embodiment]
The EUV light generation system 11 including the laser device 3 of the third embodiment will be described using FIGS. 12 and 13.
The trigger signal may include the pulse width of the trigger signal. The pulse width of the trigger signal is the time during which the excitation current is supplied to the first to fourth QCLs 311 to 314 in one pulse. In other words, the pulse width of the trigger signal may be the time width of each pulse of the excitation current supplied to the first to fourth QCLs 311 to 314.

FIG. 12 is a diagram for explaining the pulse width W ′ of the trigger signal output from the control unit 330 included in the laser apparatus 3 of the third embodiment. FIG. 13 shows the relationship between the repetition frequency of the trigger signal output to the QCL and the pulse width.
In the EUV light generation system 11 including the laser device 3 of the third embodiment, when the target repetition frequency of the EUV light 252 is changed due to a request from the exposure apparatus control unit 61, the target repetition frequency of the droplets 271 is accordingly May be changed.
In this case, in the EUV light generation system 11 according to the third embodiment, the repetition frequency of the droplet detection signal of the droplets 271 output according to the target repetition frequency of the droplets 271 may be changed. Then, the repetition frequency of the trigger signal output based on the droplet detection signal may also be changed. Thereby, the load state of each of the first to fourth QCLs 311 to 314 may change.
Therefore, the EUV light generation system 11 according to the third embodiment may cope with wavelength chirping by adjusting the pulse width W of the trigger signal.

In the EUV light generation system 11 according to the third embodiment, the configuration of the control unit 330 may be different from that of the EUV light generation system 11 according to the second embodiment shown in FIG.
The storage operation unit 332 of the control unit 330 according to the third embodiment does not have to store in advance the measurement result regarding the relationship between the light emission delay time of the QCL and the repetition frequency shown in FIG.
In the configuration and operation of the EUV light generation system 11 according to the third embodiment, the description of the same configuration and operation as in the EUV light generation system 11 according to the second embodiment shown in FIGS. 9 to 11 will be omitted.

Like the EUV light generation controller 5 according to the second embodiment, the EUV light generation controller 5 according to the third embodiment includes the target repetition frequency of the droplets 271 in the EUV light output command signal. It may be determined to have the same value as the target repetition frequency of.
Then, the EUV light generation controller 5 may generate a target supply signal with the same value as the target repetition frequency of the EUV light 252 as the target repetition frequency of the droplets 271.
Furthermore, similarly to the EUV light generation controller 5 according to the second embodiment, the EUV light generation controller 5 is based on the droplet detection signal reflecting the target repetition frequency of the EUV light 252 included in the EUV light output command signal. Alternatively, a laser output signal may be generated and output to the control unit 330.

The control unit 330 according to the third embodiment triggers each of the first to fourth QCLs 311 to 314 at a repetition frequency reflecting the target repetition frequency of the EUV light 252 in synchronization with the timing when the laser output signal is input. A signal may be output.
At this time, as shown in FIG. 12, the control unit 330 outputs the trigger signal of the pulse width W ′ at a timing delayed by a predetermined delay time Dq1 to 4 from the timing when the laser output signal is input. Good.
The pulse width W ′ of the trigger signal may be a value adjusted from the pulse width W of the trigger signal before the change in accordance with the change of the target repetition frequency of the EUV light 252.
Even if the target repetition frequency of the EUV light 252 is changed, the magnitude of the pulse width W ′ of the trigger signal is determined so that the duty ratio of the excitation current supplied to the first to fourth QCLs 311 to 314 does not change. Good.
The control unit 330 may include a storage operation unit 332 that calculates the pulse width W ′ of the trigger signal.

Here, the relationship between the wavelength chirping of the QCL and the duty ratio of the excitation current supplied to the QCL will be described.
For example, the relationship between the temperature change ΔT of the semiconductor element 3111 causing the wavelength chirping of the first QCL 311 and the duty ratio of the excitation current supplied to the first QCL 311 can be described by the following equation.
ΔT = Rth · (I · V) · D
Rth may be the thermal resistance of the semiconductor element 3111.
I may be the current value of the excitation current supplied to the semiconductor element 3111.
V may be a voltage generated in the semiconductor element 3111.
D may be a duty ratio of the excitation current supplied to the semiconductor device 3111. The duty ratio of the excitation current supplied to the semiconductor device 3111 may be the same value as the duty ratio of the trigger signal. The duty ratio of the trigger signal may be the product of the pulse width of the trigger signal and the repetition frequency.

From the above equation, it can be seen that if the thermal resistance Rth is constant, the voltage V does not change if the current value I is kept constant, and the temperature change ΔT depends on the duty ratio D.
Therefore, even if the target repetition frequency of the EUV light 252 is changed, the pulse current of the trigger signal is adjusted so that the duty ratio of the trigger signal does not change while maintaining the set value of the excitation current included in the trigger signal. The temperature change ΔT can be suppressed. For this reason, the fluctuation of the load state of the first QCL 311 can be suppressed.

Therefore, the storage operation unit 332 of the control unit 330 may store in advance the duty ratio of the trigger signal output to each of the first to fourth QCLs 311 to 314.
The duty ratio stored in storage operation unit 332 may be a constant value determined in advance by experiment or the like from the relationship with delay times Dq1 to Dq4. The duty ratio stored in the storage operation unit 332 may store a fixed value such as 40000 ns · kHz, for example.
Then, when the target repetition frequency of the EUV light 252 is changed, the storage operation unit 332 performs the following processing based on the duty ratio stored in advance to calculate the pulse width W ′ of the trigger signal. You may
For example, when the target repetition frequency of the EUV light 252 is changed from 100 kHz to 50 kHz, the storage operation unit 332 can calculate the pulse width W ′ as in the following equation.
Pulse width W '= duty ratio (40000 ns · kHz) / repetition frequency (50 kHz) = 800 ns

Alternatively, the storage operation unit 332 may store in advance a table indicating the relationship between the repetition frequency of the trigger signal and the pulse width as shown in FIG.
Then, when the target repetition frequency of the EUV light 252 is changed, the storage operation unit 332 may specify the pulse width W ′ of the trigger signal with reference to a table stored in advance.

The control unit 330 may determine the value obtained by the storage operation unit 332 as the new pulse width W ′ of the trigger signal.
Then, as shown in the lower part of FIG. 12, the control unit 330 sets the trigger signal of the newly determined pulse width W 'at the timing delayed by the delay time Dq1 to 4 from the timing when the laser output signal is input. It may be output to each of the first to fourth QCLs 311 to 314.
Thus, each of the first to fourth QCLs 311 to 314 can output pulse laser light at a repetition frequency reflecting the target repetition frequency of the EUV light 252 in synchronization with the timing when the laser output signal is input. In addition, each of the first to fourth QCLs 311 to 314 can output the pulsed laser light having the wavelength of the amplification wavelength region at substantially the same timing, with fluctuation of the load state being suppressed.
When it is preferable to use different values for each of the first to fourth QCLs 311 to 314 as the duty ratio, the storage operation unit 332 previously sets different duty ratios to different values for each of the first to fourth QCLs 311 to 314. You may memorize.

The other configuration and operation of the EUV light generation system 11 including the laser device 3 according to the third embodiment are the same as the EUV light generation system 11 including the laser device 3 according to the second embodiment shown in FIGS. It may be

As described above, the control unit 330 adjusts the pulse width W of the trigger signal to W ′ based on the target repetition frequency of the EUV light 252 requested from the exposure apparatus control unit 61 to obtain the first to fourth QCLs 311 to 314. A trigger signal can be output to each.
Therefore, in each of the first to fourth QCLs 311 to 314, even if the target repetition frequency of the EUV light 252 is changed due to a request from the exposure apparatus control unit 61, the fluctuation of the load state can be suppressed. Therefore, each of the first to fourth QCLs 311 to 314 can output pulsed laser light having a wavelength of an amplification wavelength region at substantially the same timing.
On the other hand, each of the first and second

optical switches

373 and 374 can change the optical path of the pulsed laser light 30 having the wavelength of the amplification wavelength region at a repetition frequency reflecting the target repetition frequency of the EUV light 252. Each of the regenerative amplifier 370 and the first to fourth amplifiers 351 to 354 can appropriately amplify and output the pulse laser beam 30 at a repetition frequency reflecting the target repetition frequency of the EUV light 252.
Thus, when the target repetition frequency of the EUV light 252 is changed, the laser device 3 of the third embodiment can output the pulse laser light 31 at a repetition frequency reflecting the target repetition frequency of the EUV light 252. In addition, the laser apparatus 3 of the third embodiment is a pulse laser appropriately amplified while suppressing fluctuations in the load states of the first to fourth QCLs 311 to 314 even when the target repetition frequency of the EUV light 252 is changed. Light 31 can be output.
Therefore, the laser device 3 of the third embodiment appropriately amplifies the pulsed laser beam 30 even when the operating conditions are changed, and outputs the pulsed laser beam 31 having the desired characteristics at a desired timing. It can.

[9. Other]
[9.1 Hardware environment of each control unit]
Those skilled in the art will appreciate that a general purpose computer or programmable controller can be combined with program modules or software applications to implement the subject matter described herein. Generally, program modules include routines, programs, components, data structures, etc. that can perform the processes described in this disclosure.

FIG. 14 is a block diagram illustrating an exemplary hardware environment in which various aspects of the disclosed subject matter can be implemented. The exemplary hardware environment 100 of FIG. 14 includes a processing unit 1000, a storage unit 1005, a user interface 1010, a parallel I / O controller 1020, a serial I / O controller 1030, A / D, D / A. Although the converter 1040 may be included, the configuration of the hardware environment 100 is not limited to this.

The processing unit 1000 may include a central processing unit (CPU) 1001, a memory 1002, a timer 1003, and an image processing unit (GPU) 1004. Memory 1002 may include random access memory (RAM) and read only memory (ROM). The CPU 1001 may be any commercially available processor. Dual microprocessors or other multiprocessor architectures may be used as the CPU 1001.

These components in FIG. 14 may be interconnected to perform the processes described in this disclosure.

In operation, the processing unit 1000 may read and execute a program stored in the storage unit 1005, and the processing unit 1000 may read data from the storage unit 1005 together with the program, and processing The unit 1000 may write data to the storage unit 1005. The CPU 1001 may execute a program read from the storage unit 1005. The memory 1002 may be a work area for temporarily storing a program executed by the CPU 1001 and data used for the operation of the CPU 1001. The timer 1003 may measure a time interval and output the measurement result to the CPU 1001 according to the execution of the program. The GPU 1004 may process image data according to a program read from the storage unit 1005, and may output the processing result to the CPU 1001.

The parallel I / O controller 1020 is connected to parallel I / O devices that can communicate with the processing unit 1000, such as the exposure apparatus control unit 61, the EUV light generation control unit 5, the laser light traveling direction control unit 34, and the control unit 330. And control communication between the processing units 1000 and their parallel I / O devices. The serial I / O controller 1030 includes first to fourth RF power supplies 361 to 364, RF power supplies 380, first to fourth

optical switches

321, 322, 373 and 374, target supply unit 26, first to fourth QCLs 311 to 314, etc. , And may be connected to a serial I / O device capable of communicating with the processing unit 1000, and may control communication between the processing unit 1000 and those serial I / O devices. The A / D, D / A converter 1040 may be connected to an analog device such as a temperature sensor, a pressure sensor, various gauge sensors, and a target sensor 4 via an analog port, and the processing unit 1000 and those analog devices Control of the communication between them, and A / D and D / A conversion of communication contents may be performed.

The user interface 1010 may display the progress of the program executed by the processing unit 1000 to the operator so that the operator can instruct the processing unit 1000 to stop the program or execute the interrupt routine.

The exemplary hardware environment 100 may be applied to the configurations of the exposure apparatus control unit 61, the EUV light generation control unit 5, the laser light traveling direction control unit 34, and the control unit 330 in the present disclosure. Those skilled in the art will appreciate that the controllers may be implemented in a distributed computing environment, ie, an environment where tasks are performed by processing units that are linked through a communications network. In the present disclosure, the exposure apparatus control unit 61, the EUV light generation control unit 5, the laser light traveling direction control unit 34, and the control unit 330 may be connected to one another via a communication network such as Ethernet or the Internet. In a distributed computing environment, program modules may be stored on both local and remote memory storage devices.

[9.2 Modification of laser apparatus related to generation of trigger signal]
As described above, the trigger signal may be a signal that gives the opportunity for the first to fourth QCLs 311 to 314 to perform laser oscillation and to output pulsed laser light. The trigger signal may include the set value of the excitation current supplied to each of the first to fourth QCLs 311 to 314. The pulse width of the trigger signal may be the time width of each pulse of the excitation current supplied to the first to fourth QCLs 311 to 314.
In the laser device 3 of the first to third embodiments, the control unit 330 generates the trigger signal output to each of the first to fourth QCLs 311 to 314, but the laser device 3 of the present disclosure is not limited to this. .
In the laser device 3 of the present disclosure, the control unit 330 may cause each of the first to fourth QCL control units included in each of the first to fourth QCLs 311 to 314 to generate a trigger signal.
That is, the laser device 3 of the present disclosure can adopt the following modification with regard to the generation of the trigger signal.

The modification of the laser apparatus 3 regarding the production | generation of a trigger signal is demonstrated using FIG.
FIG. 15 shows a diagram for explaining a modified example of the laser device 3 regarding generation of a trigger signal.
In the description of FIG. 15, the first QCL 311 will be described as an example.

The control unit 330 included in the laser device 3 of the modification outputs the set value regarding the current value and time width of the excitation current and the output timing signal to each of the first to fourth QCL control units instead of the trigger signal. It is also good.
The output timing signal may be a signal indicating that it is the timing at which pulse laser light is output from each of the first to fourth QCLs 311 to 314. Similar to the trigger signal, predetermined delay times Dq 1 to Dq 4 and Dq 1 ′ to Dq 4 ′ may be added to the output timing signal and output from the control unit 330.
The set values regarding the current value and the time width of the excitation current may be set values that determine the current value and the time width in the pulse waveform of the excitation current supplied to the semiconductor elements of the first to fourth QCLs 311 to 314. The time width of the excitation current at the setting value may define the pulse width W or the pulse width W ′ of the trigger signal.

As shown in FIG. 15, the first QCL 311 provided in the laser device 3 of the modification example includes a semiconductor element 3111, a Peltier element 3112, a temperature sensor 3113, a current controller 3114, a temperature control unit 3115, and a first QCL control. Part 3116 may be included.

The first QCL control unit 3116 may receive a set value related to the current value and the time width of the excitation current supplied to the first QCL 311 output from the control unit 330.
The first QCL control unit 3116 may generate a trigger signal having a pulse waveform of the excitation current according to the current value and the time width in the input setting value.
The output timing signal for the first QCL 311 output from the control unit 330 may be input to the first QCL control unit 3116.
The first QCL control unit 3116 may output the generated trigger signal to the current controller 3114 in response to the input output timing signal.
The first QCL control unit 3116 may output a temperature setting value for setting the temperature of the semiconductor element 3111 to a predetermined temperature to the temperature control unit 3115.

The trigger signal output from the first QCL control unit 3116 may be input to the current controller 3114.
The current controller 3114 may supply an excitation current corresponding to the pulse waveform of the input trigger signal to the pair of electrode layers provided in the semiconductor element 3111.
An excitation current corresponding to the trigger signal can flow through the semiconductor layers 3111 b and 3111 c and the active layer 3111 a sandwiched by the pair of electrode layers.

The temperature sensor 3113 may detect the temperature of the semiconductor element 3111 and output a detection signal to the temperature control unit 3115.

The temperature set value output from the first QCL control unit 3116 may be input to the temperature control unit 3115.
The detection signal output from the temperature sensor 3113 may be input to the temperature control unit 3115.
Even if the temperature control unit 3115 outputs a signal for controlling the cooling operation of the Peltier element 3112 to the Peltier element 3112 so that the temperature detection value indicated by the input detection signal approaches the input temperature setting value. Good.

With the above configuration, the first QCL 311 included in the laser device 3 of the modified example generates a trigger signal in the first QCL control unit 3116 under the control of the control unit 330, and the excitation current corresponding to the trigger signal is sent to the semiconductor element 3111. It can be supplied. Thereby, the first QCL 311 included in the laser device 3 of the modified example can output pulsed laser light from the semiconductor element 3111 under the control of the control unit 330.

The configurations of the semiconductor element 3111 and the Peltier element 3112 shown in FIG. 15 may be the same as those of the semiconductor element 3111 and the Peltier element 3112 shown in FIG.
The second to fourth QCLs 312 to 314 included in the laser device 3 of the modification may also be configured in the same manner as the first QCL 311 shown in FIG.

[9.3 Other Modifications]
The EUV light generation controller 5 and the controller 330 may be configured as an integrated controller by combining some or all of them.

It will be apparent to those skilled in the art that the embodiments described above can apply each other's techniques to each other including variations.

For example, the control unit 330 and the first to fourth QCLs 311 to 314 included in the laser device 3 of the modified example are respectively included in the control unit 330 and the first to fourth QCLs 311 to 314 included in each of the laser devices 3 of the first to third embodiments. It may be applied.

The above description is intended to be illustrative only and not limiting. Thus, it will be apparent to one skilled in the art that changes can be made to the embodiments of the present disclosure without departing from the scope of the appended claims.

The terms used throughout the specification and the appended claims should be construed as "non-limiting" terms. For example, the terms "include" or "included" should be interpreted as "not limited to what is described as included." The term "having" should be interpreted as "not limited to what has been described as having." Also, the modifier "one", as described in this specification and in the appended claims, should be interpreted to mean "at least one" or "one or more".

1 ... EUV light generation device 2 ... Chamber 27 ... Target 3 ... Laser device 311 to 314 ... 1st to 4th QCL
321, 322 ... first and second optical switches 330 ...

control section

373, 374 ... third and fourth optical switches

Claims

What is claimed is: 1. A laser apparatus for use with an extreme ultraviolet light generator that generates extreme ultraviolet light at a preset repetition frequency, comprising:
A semiconductor laser that outputs a laser beam when a trigger signal is input;
An optical switch disposed on the optical path of the laser beam to switch whether to pass the laser beam;
Outputting the trigger signal to the semiconductor laser at a frequency that is an integral multiple of the repetition frequency;
Controlling the optical switch such that the laser beam passes at the repetition frequency;
Laser device.
What is claimed is: 1. A laser apparatus for use with an extreme ultraviolet light generator that generates extreme ultraviolet light at a preset repetition frequency, comprising:
A semiconductor laser that outputs a laser beam when a trigger signal is input;
An optical switch disposed on the optical path of the laser beam to switch whether to pass the laser beam;
The output timing of the trigger signal output to the semiconductor laser in synchronization with the repetition frequency is changed based on the repetition frequency,
Controlling the optical switch such that the laser beam passes at the repetition frequency;
Laser device.
What is claimed is: 1. A laser apparatus for use with an extreme ultraviolet light generator that generates extreme ultraviolet light at a preset repetition frequency, comprising:
A semiconductor laser that outputs a laser beam when a trigger signal is input;
An optical switch disposed on the optical path of the laser beam to switch whether to pass the laser beam;
Changing a pulse width of the trigger signal output to the semiconductor laser in synchronization with the repetition frequency based on the repetition frequency;
Controlling the optical switch such that the laser beam passes at the repetition frequency;
Laser device.
The laser device according to claim 1, further comprising: a regenerative amplifier that amplifies the laser light output from the semiconductor laser and includes the optical switch.
The laser device according to claim 2, further comprising: a regenerative amplifier that amplifies the laser light output from the semiconductor laser and includes the optical switch.
The laser device according to claim 3, further comprising: a regenerative amplifier that amplifies the laser light output from the semiconductor laser and includes the optical switch.
A semiconductor laser that outputs a laser beam when a trigger signal is input;
An optical switch disposed on the optical path of the laser beam to switch whether to pass the laser beam;
Outputting the trigger signal to the semiconductor laser at a frequency that is an integral multiple of the repetition frequency;
Controlling the optical switch such that the laser beam passes at the repetition frequency;
A target supply unit that supplies a target that emits extreme ultraviolet light when irradiated with the laser light, to a chamber into which the laser light that has passed through the optical switch is introduced, at a frequency that is an integral multiple of the repetition frequency ,
Extreme ultraviolet light generating device comprising: